Transmission device, reception device, communication system, transmission method, reception method, and communication method

ABSTRACT

Provided is a device, which is a transmission device that can improve performance, that includes: a light source; and a transmitter that generates a modulated signal based on an input signal and transmits the modulated signal from the light source as visible light by changing a luminance of the light source in accordance with the modulated signal. The transmitter includes, in the modulated signal, a plurality of items of information related to service set identifiers (SSIDs) of a plurality of mutually different access points in a wireless local area network (LAN), and transmits the modulated signal from the light source.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.16/916,672, filed Jun. 30, 2020, which is divisional of U.S. applicationSer. No. 16/380,458, filed Apr. 10, 2019, now U.S. Pat. No. 10,742,319,which is a U.S. continuation application of PCT International PatentApplication Number PCT/JP2017/036597 filed on Oct. 10, 2017, claimingthe benefit of priority of U.S. Provisional Patent Application No.62/407,003 filed on Oct. 12, 2016 and U.S. Provisional PatentApplication No. 62/411,035 filed on Oct. 21, 2016. The entiredisclosures of the above-identified applications, including thespecifications, drawings and claims are incorporated herein by referencein their entirety.

FIELD

The present disclosure relates to a transmission device, a receptiondevice, a communication system, a transmission method, a receptionmethod, and a communication method.

BACKGROUND

Devices can use global positioning system (GPS) as a method forobtaining location information. In such cases, devices receive amodulated signal transmitted from a satellite, and estimate location bypositioning calculation. However, it is difficult for the device toestimate location information when the device is indoors, wherereception of the radio waves transmitted by the GPS satellite isdifficult.

For example, one method for overcoming such a problem is disclosed innon-patent literature (NPTL) 1. As disclosed in NPTL 1, there is amethod by which the device uses radio waves transmitted from an accesspoint in a wireless local area network (LAN) to estimate location.

CITATION LIST Non-Patent Literature

-   [Non-Patent Literature 1]-   Santosh Pandey, “NGP Use Case Template” IEEE802.11-16/0137 r4,    2016-03-12

SUMMARY Technical Problem

However, the performance of the transmission device and the receptiondevice can be improved upon.

Solution to Problem

A transmission device according to one aspect of the present disclosureincludes: a light source; and a transmitter that generates a modulatedsignal based on an input signal and transmits the modulated signal fromthe light source as visible light by changing a luminance of the lightsource in accordance with the modulated signal. The modulated signalincludes a plurality of items of information related to service setidentifiers (SSIDs) of a plurality of mutually different access pointsin a wireless local area network (LAN).

Additional benefits and advantages of the disclosed embodiments will beapparent from the Specification and Drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the Specification and Drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

Advantageous Effects

According to the present disclosure, it is possible to improve upon theperformance of a communication device and a reception device.

BRIEF DESCRIPTION OF DRAWINGS

These and other objects, advantages and features of the disclosure willbecome apparent from the following description thereof taken inconjunction with the accompanying drawings that illustrate a specificembodiment of the present disclosure.

FIG. 1 illustrates one example of a configuration of a device and aterminal according to Embodiment 1.

FIG. 2 illustrates one example of a frame configuration transmitted in amodulated signal transmitted by a first device according to Embodiment1.

FIG. 3 illustrates one example including a plurality of devicesaccording to Embodiment 2.

FIG. 4 illustrates one example of a configuration of a device and aterminal according to Embodiment 3.

FIG. 5 illustrates one detailed example of a screen of a displayaccording to Embodiment 3.

FIG. 6 illustrates one example of a frame configuration of a modulatedsignal transmitted by a first device according to Embodiment 3.

FIG. 7 illustrates one example of a frame configuration of a modulatedsignal transmitted by a base station according to Embodiments 3 through6.

FIG. 8 is a flow chart of one example of processes performed by adevice, terminal, and base station according to Embodiment 3.

FIG. 9 illustrates one example of a map according to Embodiment 3.

FIG. 10 illustrates one example of a configuration of a communicationsystem according to Embodiment 4.

FIG. 11 illustrates one example of a frame configuration of a modulatedsignal transmitted by a second device according to Embodiment 4.

FIG. 12 illustrates one example of a frame configuration of a modulatedsignal transmitted by a radio device included in a terminal according toEmbodiment 4.

FIG. 13 is a flow chart of one example of processes performed by adevice, terminal, and base station according to Embodiment 4.

FIG. 14 illustrates one example of a configuration of devices, aterminal, and a base station according to Embodiment 5.

FIG. 15 illustrates one example of a frame configuration of a modulatedsignal transmitted by a third device according to Embodiment 5.

FIG. 16 illustrates one example of a frame configuration of a modulatedsignal transmitted by a fourth device according to Embodiment 5.

FIG. 17 is a flow chart of a first example of processes performed by athird device, a fourth device, a terminal, and a base station accordingto Embodiment 5.

FIG. 18 is a flow chart of a second example of processes performed by athird device, a fourth device, a terminal, and a base station accordingto Embodiment 5.

FIG. 19 illustrates a space in which a third device, a fourth device, aterminal, and a base station according to Embodiment 5 are disposed.

FIG. 20 illustrates one example of a configuration of a communicationsystem according to Embodiment 6.

FIG. 21 is a flow chart of one example of processes performed by anelement related to, for example, an LED, a terminal, and a radio deviceincluded in a base station according to Embodiment 6.

FIG. 22 illustrates one example of a configuration of a communicationsystem according to Embodiment 7.

FIG. 23 illustrates one example of a frame configuration of a modulatedsignal transmitted by a device according to Embodiment 7.

FIG. 24 illustrates one example of another frame configuration of amodulated signal transmitted by a device according to Embodiment 7.

FIG. 25 illustrates one example of another frame configuration of amodulated signal transmitted by a device according to Embodiment 7.

FIG. 26 illustrates one example of transmission method using a deviceaccording to Embodiment 7.

FIG. 27 illustrates one example of an area in which devices and basestations are disposed according to Embodiment 7.

FIG. 28 is a flow chart of one example of processes performed by adevice, terminal, and base station according to Embodiment 7.

FIG. 29 illustrates one example of an automobile including a lightsource.

FIG. 30 illustrates one example of an automobile including a lightreceiver.

FIG. 31 illustrates another example of a communication method.

FIG. 32 illustrates one example of line scan sampling.

FIG. 33 illustrates an example of a captured image in which a stripedpattern does not appear.

FIG. 34 illustrates an example of a captured image in which a stripedpattern appears.

FIG. 35A illustrates one example of a 4 PPM modulation scheme.

FIG. 35B illustrates one example of a Manchester coding scheme.

DESCRIPTION OF EMBODIMENTS

Underlying Knowledge Forming Basis of the Present Disclosure

Devices can use global positioning system (GPS) as a method forobtaining location information. In such cases, devices receive amodulated signal transmitted from a satellite, and estimate location bypositioning calculation. However, it is difficult for the device toestimate location information when the device is indoors, wherereception of the radio waves transmitted by the GPS satellite isdifficult.

For example, one method for overcoming such a problem is disclosed inNPTL 1 described above. As disclosed in NPTL 1, there is a method bywhich the device uses radio waves transmitted from an access point in awireless local area network (LAN) to estimate location. However, sinceit is not easy to know the service set identifier (SSID) of an accesspoint that can be securely accessed, when the device attempts to obtainlocation information, there is a possibility that the device willconnect to an insecure SSID access point, leading to the possibility ofa compromise of information.

In view of this, in the present disclosure, a (optical) modulated signalincluding information related to a location is transmitted, for example,from, for example, a light emitting diode (LED) lamp, light source, orlight that is provided in a room and emits visible light. For example, aterminal (device) receives a (optical) modulated signal via, forexample, an image sensor such as a complementary metal oxidesemiconductor (CMOS) or organic photoconductive film (OPF) CMOS (i.e.,organic CMOS) image sensor, performs demodulation and such, and obtainsat least the information related to a location. With this, the terminalcan achieve the advantageous effect of being able to securely obtaininformation related to a location.

Alternatively, in the present disclosure, for example, a (optical)modulated signal including information related to an SSID istransmitted, for example, from, for example, a light emitting diode(LED) lamp, light source, or light that is provided in a room and emitsvisible light. A terminal (device) receives a (optical) modulated signalvia, for example, an image sensor such as a complementary metal oxidesemiconductor (CMOS) or organic photoconductive film (OPF) CMOS (i.e.,organic CMOS) image sensor, performs demodulation and such, and obtainsat least the information related to the SSID. With this, the terminalcan achieve the advantageous effect of being able to securely connect toan access point.

Embodiment 1

FIG. 1 illustrates one example of configurations of device 100including, for example, a light emitting diode (LED) light source, lamp,light source, and/or light that emits visible light, and terminal 150.Device 100 includes, for example, a light emitting diode (LED) lamp,light source, and/or light that emits visible light. Note that thisdevice is referred to as a “first device”.

Transmitter 102 receives an input of information related to a locationor information 101 related to a position. Moreover, transmitter 102 mayreceive an input of information 105 related to a time. Moreover,transmitter 102 may receive an input of both (i) the information relatedto a location or information 101 related to a position and (ii)information 105 related to a time.

Transmitter 102 receives an input of information related to a locationor information 101 related to a position and/or information 105 relatedto a time, and based on the one or more input signals, generates a(optical) modulated signal, and outputs modulated signal 103. Forexample, modulated signal 103 is transmitted from light source 104.

Next, examples of the information related to a location or information101 related to a position will be given.

Example 1

Information related to a location or information 101 related to aposition may be information indicating the latitude and/or longitude ofa location or position. For example, the information related to alocation or information 101 related to a position may be informationindicating “45 degrees north latitude, 135 degrees east longitude”.

Example 2

Information related to a location or information 101 related to aposition may be information indicating an address. For example, theinformation related to a location or information 101 related to aposition may be information indicating “1-1-1 XYZ-machi, Chiyoda-ku,Tokyo-to”.

Example 3

Information related to a location or information 101 related to aposition may be information indicating a building or facility, forexample. For example, the information related to a location orinformation 101 related to a position may be information indicating“Tokyo Tower”.

Example 4

Information related to a location or information 101 related to aposition may be information indicating a fixed location or position ofsomething at a building or facility, for example.

For example, assume there are five parking spaces for automobiles in aparking lot. Assume the first through fifth parking spaces are named A-1through A-5, respectively. In this example, the information related to alocation or information 101 related to a position may be informationindicating, for example, “A-3”.

This example is not limited to only parking spaces in a parking lot.

Information related to a location or information 101 related to aposition may be for example, information related to a section, a seat, astore, a facility, etc., at, for example, a concert facility, a stadiumsuch as a baseball, soccer, or tennis stadium, an airplane, an airportlounge, a railway, a station, etc.

Note that methods for configuring the information related to a locationor information 101 related to a position are not limited to the aboveexamples.

Terminal 150 receives the modulated signal transmitted by first device100.

Light receiver 151 is, for example, a CMOS or organic CMOS image sensor.Light receiver 151 receives light including the modulated signal outputfrom the first device, and outputs reception signal 152. Receiver 153receives an input of reception signal 152, performs processing such asdemodulation and error correction decoding on the modulated signalincluded in the reception signal, and outputs reception data 154.

Note that reception signal 152 output from light receiver 151 may be asignal including information on an image or moving picture obtained bythe image sensor, and may be an output signal from an element thatperforms photo-electric conversion (an element that converts light intoan electric signal). In the following description, when a reception-sidedevice is described as receiving a modulated signal without giving anyfurther details on the processes performed by light receiver 151, thismeans that the reception-side device obtains a signal of an image ormoving picture and a modulated signal for transmitting information byphoto-electric conversion (converting light into an electric signal) oflight including the modulated signal by light receiver 151. However, themethod described above used to receive the modulated signal by thereception-side device is merely one non-limiting example.

Data analyzer 155 receives an input of reception data 154, estimates,for example, the location or position of terminal 150 from receptiondata 154, and outputs information 156 including at least information onthe location or position of terminal 150.

Display 157 receives an input of information 156, and displaysinformation related to the location or position of terminal 150 based onthe location or position of terminal 150 included in information 156.

FIG. 2 illustrates one example of a configuration of a frame transmittedin a modulated signal transmitted by first device 100. In FIG. 2 , timeis represented on the horizontal axis. For example, the first devicetransmits preamble 201 and then transmits control information symbol202, symbol 203 related to location information or position information,and symbol 204 related to time information.

Here, preamble 201 is a symbol for terminal 150, which receives themodulated signal transmitted by first device 100, to perform, forexample, signal detection, temporal synchronization, and/or framesynchronization.

Control information symbol 202 is, for example, a symbol including dataon, for example, the configuration method of the modulated signal, theerror correction encoding scheme used, and/or the frame configurationmethod.

Symbol 203 related to location information or position information is asymbol including information related to a location or informationrelated to a position illustrated in FIG. 1 .

The frame may include symbols other than symbols 201, 202, and 203. Forexample, as illustrated in FIG. 2 , the frame may include symbol 204related to time information. Symbol 204 related to time informationincludes, for example, information indicating a time of transmission ofthe modulated signal by the first device. Note that the frameconfiguration of the modulated signal transmitted by the first device isnot limited to the frame configuration illustrated in FIG. 2 . Moreover,the symbols included in the modulated signal are not limited to theconfiguration illustrated in FIG. 2 (the modulated signal may includesymbols including other data and/or information).

Next, the advantageous effects achieved when the first device transmitsa modulated signal and the terminal receives the modulated signal, asdescribed with reference to FIG. 1 and FIG. 2 , will be described.

Since the first device transmits the modulated signal via visible light,a terminal capable of receiving the modulated signal is not in alocation significantly far from the location of the first device.Accordingly, by the terminal obtaining the location or positioninformation transmitted by the first device, the terminal can achieve anadvantageous effect whereby it is possible to easily (i.e., withouthaving to perform complicated signal processing) obtain accurateposition information. Moreover, when the first device is disposed in aplace where reception of satellite radio waves from a GPS satellite isdifficult, it is possible to achieve an advantageous effect whereby itis possible for the terminal to securely obtain accurate positioninformation even in locations in which reception of radio waves from aGPS satellite is difficult, by the terminal receiving the modulatedsignal transmitted by the first device.

Embodiment 2

In this embodiment, a configuration in which a plurality of the firstdevices described in Embodiment 1 are provided will be described.

In this embodiment, for example, as illustrated in FIG. 3 , first device#1 301-1 having the same configuration as first device 100 illustratedin FIG. 1 transmits a modulated signal, and terminal 302 receives themodulated signal. Terminal 302 receives the modulated signal transmittedby first device #1 301-1, and obtains, for example, information relatedto first location or position #1 and information related to first time#1.

Similarly, first device #2 301-2 having the same configuration as firstdevice 100 illustrated in FIG. 1 transmits a modulated signal, andterminal 302 receives the modulated signal. Terminal 302 receives themodulated signal transmitted by first device #2 301-2, and obtains, forexample, information related to first location or position #2 andinformation related to first time #2.

With this, terminal 302 can know the distance between first device #1301-1 and first device #2 301-2 illustrated in FIG. 3 from theinformation related to first location or position #1 and the informationrelated to first location or position #2. Moreover, terminal 302 canknow the distance between terminal 302 and first device #1 301-1 basedon the information related to first time #1, and, for example, the timeat which the terminal receives the modulated signal transmitted by firstdevice #1 301-1. Similarly, terminal 302 can know the distance betweenterminal 302 and first device #2 301-2 based on the information relatedto first time #2, and, for example, the time at which the terminalreceives the modulated signal transmitted by first device #2 301-2.

Moreover, terminal 302 knows the position of first device #1 from theinformation related to the first location or position #1. Moreover,terminal 302 knows the position of first device #2 from the informationrelated to the first location or position #2. Terminal 302 knows thegeometry of the triangle formed by first device #1 301-1, first device#2 301-2, and terminal 302 from the distance between first device #1301-1 and first device #2 301-2, the distance between first device #1301-1 and the terminal, and the distance between first device #2 301-2and the terminal.

Accordingly, terminal 302 can accurately calculate and obtain theposition of terminal 302 from the position of the first device #1, theposition of the first device #2, and the geometry of the triangle formedby first device #1 301-1, first device #2 301-2, and terminal 302.

However, the geodetic measurement method used by terminal 302 to obtainthe location or position information is not limited to the methoddescribed above; any geodetic measurement method may be used. Examinesof geodetic measurement methods include triangulation, traversecalculation, leveling, etc.

As described above, the terminal can obtain the above-describedinformation from a plurality of devices including light sources thattransmit location information, and as a result, it is possible toachieve an advantageous effect whereby the terminal can accuratelyestimate position. Moreover, as described in Embodiment 1, when thedevice including a light source that transmits location information isdisposed in a place where reception of satellite radio waves from a GPSsatellite is difficult, it is possible to achieve an advantageous effectwhereby it is possible for the terminal to securely obtain accurateposition information even in locations in which reception of radio wavesfrom a GPS satellite is difficult, by the terminal receiving themodulated signal transmitted by the device.

Note that in the above example, the terminal receives modulated signalstransmitted by two devices, but an embodiment in which the terminalreceives modulated signals transmitted by more than two devices can beimplemented in the same manner. Note that the more devices there are,the more accurately the terminal can calculate the position information,so from this viewpoint, more devices are more beneficial.

Embodiment 3

FIG. 4 illustrates one example of configurations of; a device including,for example, an LED light source, lamp, light source, and/or light thatemits visible light; a terminal; and, for example, a base station thatcommunicates with the terminal. Device 400 in FIG. 4 includes, forexample, an LED lamp, light source, and/or light that emits visiblelight. Note that the device is referred to as a “first device”. In firstdevice 400 in FIG. 4 , elements that operate the same as in first device100 in FIG. 1 share like reference marks.

Terminal 450 in FIG. 4 indicates the configuration of a terminal, andelements that are the same as in FIG. 1 share like reference marks.

In first device 400 in FIG. 4 , transmitter 102 receives inputs of, forexample, information related to a location or information 101 related toa position, information 401-1 related to a service set identifier(SSID), and information 401-2 related to an access destination.Moreover, transmitter 102 may receive an input of information 105related to a time.

Transmitter 102 receives inputs of information related to a location orinformation 101 related to a position, information 401-1 related to anSSID, information 401-2 related to an access destination, and/orinformation 105 related to a time, and based on the one or more inputsignals, generates a (optical) modulated signal, and outputs modulatedsignal 103. For example, modulated signal 103 is transmitted from lightsource 104.

Note that since examples of the information related to a location orinformation 101 related to a position are the same as described inEmbodiment 1, repeated description will be omitted.

Next, information 401-1 related to an SSID and information 401-2 relatedto an access destination will be described.

First, information 401-1 related to an SSID will be described.

Information 401-1 related to an SSID is information indicating the SSIDof the base station (or access point (AP)) 470 illustrated in FIG. 4 .When processing is performed for determining whether or not the SSIDnotified via the optical signal is the SSID of a secure base station,first device 400 can provide access to base station 470, which is asecure access destination for terminal 450. With this, terminal 450 inFIG. 4 can achieve the advantageous effect of being able to securelyobtain information from base station (or AP) 470. On the other hand,first device 400 can restrict the terminals that access base station 470to terminals in a space in which it is possible to receive opticalsignals transmitted (emitted) by first device 400.

Note that when terminal 450 receives an optical signal transmitted via apredetermined scheme, it may be determined that the notified SSID is theSSID of a secure base station, and, alternatively, processing fordetermining whether the SSID is secure or not may be performed. Forexample, first device 400 may transmit a predetermined identifier in anoptical signal, and the terminal may determine whether the notified SSIDis the SSID of a secure base station or not based on the receivedidentifier. Alternatively, the processing for determining whether thebase station is secure or not may be omitted by terminal 450, andinstead, the user may select a first device 400 that is highly secureutilizing the characteristics of the visible light, and the SSID of thehighly secure base station may be obtained by terminal 450 receiving theoptical signal from first device 400.

Note that although FIG. 4 only illustrates base station (or AP) 470, forexample, when there is a base station (or AP) other than base station(or AP) 470, terminal 450 in FIG. 4 accesses base station (or AP) 470 toobtain information.

Information 401-2 related to an access destination is informationrelated to an access destination for terminal 450 in FIG. 4 to accessbase station (or AP) 470 and then obtain information (note that aspecific example of operations will be given later).

Terminal 450 in FIG. 4 receives the modulated signal transmitted byfirst device 400. Note that in terminal 450 in FIG. 4 , operations thatare the same as in terminal 150 in FIG. 1 share like reference marks.

Light receiver 151 included in terminal 450, examples of which includean image sensor such as a CMOS or organic CMOS image sensor, receivesthe modulated signal transmitted by first device 400. Receiver 153receives an input of reception signal 152 received by light receiver151, performs processing such as demodulation and error correctiondecoding on the reception signal, and outputs reception data 154.

Data analyzer 155 receives an input of reception data 154, estimates,for example, the location or position of the terminal from receptiondata 154, and outputs information 156 including at least information onthe location or position of the terminal, information 451 related to anSSID, and information 452 related to an access destination.

Display 157 receives inputs of information 156 including information onthe location or position of the terminal, information 451 related to anSSID, and information 452 related to an access destination, and, forexample, displays the location or position of the terminal, the SSID ofa communication partner that radio device 453 included in terminal 450accesses, and the access destination (this display is referred to as a“first display”).

For example, after the first display, radio device 453 included interminal 450 in FIG. 4 receives inputs of information 451 related to anSSID and information 452 related to an access destination. Then, radiodevice 453 included in terminal 450 in FIG. 4 connects to thecommunication partner by using, for example, radio waves, based oninformation 451 related to an SSID. Note that in the example illustratedin FIG. 4 , radio device 453 included in terminal 450 in FIG. 4 connectsto base station 470.

Then, based on information 452 related to an access destination, radiodevice 453 included in terminal 450 in FIG. 4 generates a modulatedsignal from data including the information related to an accessdestination, and transmits the generated modulated signal to basestation 470 over, for example, radio waves.

Base station (or AP) 470, which is the communication partner of theterminal in FIG. 4 , receives the modulated signal transmitted by radiodevice 453 included in terminal 450 in FIG. 4 . Then, base station (orAP) 470 performs processing such as demodulation and error correctiondecoding on the received modulated signal, outputs reception data 471including information on the access destination transmitted by terminal450 in FIG. 4 , and based on the information on the access destination,base station (or AP) 470 accesses a desired access destination over anetwork and, for example, obtains desired information 472 from theaccess destination.

Then, base station 470 receives an input of the desired information 472,generates a modulated signal from the desired information 472, andtransmits the modulated signal to terminal 450 in FIG. 4 over, forexample, radio waves. Radio device 453 in terminal 450 in FIG. 4receives the modulated signal transmitted by base station 470, performsprocessing such as demodulation and error correction decoding, andobtains the desired information 472.

For example, assume the desired information 472 is information relatedto a section, a seat, a store, a facility, etc., on/at, for example, amap, a map or floor guide for a building, a map or floor guide for afacility, a map or floor guide for a parking lot, a concert facility, astadium such as a baseball, soccer, or tennis stadium, an airplane, anairport lounge, a railway, a station, etc.

Display 157 receives inputs of the desired information 472, information156 including, at least information on the location or position of theterminal, information 451 related to an SSID, and after the firstdisplay, displays a result of mapping the position of the terminal onthe display of the map, floor guide, facility information, seatinformation, or store information, based on the desired information 472and information 156 including at least information on the location orposition of the terminal.

A specific example will be given. FIG. 5 illustrates one example of adisplay displayed by display 157. The display in FIG. 5 indicates thatthis is the third floor of a building. Each of A-1, A-2, A-3, A-4, A-21,A-22, A-23, and A-24 indicates a position of a parking space for anautomobile. B-1 and B-2 indicate positions of elevators. The informationon this map is the desired information 472. As illustrated in FIG. 5 ,the “current location” is mapped on the map. Here, the current locationis information obtained from information 156 including at leastinformation on the location or position of the terminal.

FIG. 6 illustrates one example of a configuration of a frame of amodulated signal transmitted by first device 400 in FIG. 4 . In FIG. 6 ,time is represented on the horizontal axis, and symbols that transmitthe same information as indicated in FIG. 2 share like reference marks.Accordingly, repeated description will be omitted

First device 400 transmits symbol 600-1 related to an SSID and symbol600-2 related to an access destination in addition to preamble 201,control information symbol 202, symbol 203 related to locationinformation or position information, and symbol 204 related to timeinformation.

Note that symbol 600-1 related to an SSID is a symbol for transmittinginformation 401-1 related to an SSID illustrated in FIG. 4 , and symbol600-2 related to an access destination is a symbol for transmittinginformation 401-2 related to an access destination in FIG. 4 . Note thatin the frame illustrated in FIG. 6 , symbols other than the symbolsshown in FIG. 6 may be included. Moreover, the frame configuration,including the order in which the symbols are transmitted, is not limitedto the configuration illustrated in FIG. 6 .

FIG. 7 illustrates one example of a frame configuration of a modulatedsignal transmitted by base station 470 illustrated in FIG. 4 . Time isrepresented on the horizontal axis. As illustrated in FIG. 7 , basestation 470 transmits, for example, preamble 701, and then transmitscontrol information symbol 702 and information symbol 703.

Here, preamble 701 is a symbol for the terminal, which receives themodulated signal transmitted by base station 470, to perform, forexample, signal detection, temporal synchronization, framesynchronization, and/or frequency offset estimation.

Control information symbol 702 includes, for example, informationrelated to the error correction encoding scheme method and/ordemodulation scheme used in the generation of the modulated signal, andinformation related to frame configuration.

Information symbol 703 is a symbol for transmitting information. Notethat in this embodiment, information symbol 703 is a symbol fortransmitting the desired information 472 described above.

Note that base station 470 in FIG. 4 may transmit a frame includingsymbols other than the symbols illustrated in FIG. 7 (for example, aframe including a pilot symbol (reference symbol) midway through theinformation symbol). Moreover, the frame configuration, including theorder in which the symbols are transmitted, is not limited to theconfiguration illustrated in FIG. 7 . In FIG. 7 , a plurality of symbolsmay be present along the frequency axis, that is to say, symbols may bepresent on a plurality of frequencies (a plurality of carriers).

Moreover, for example, a modulated signal that has the frameconfiguration illustrated in FIG. 6 and is transmitted by the firstdevice being transmitted at a regular timing, e.g., repeatedlytransmitted is conceivable. This makes it possible for a plurality ofterminals to implement the operations described above.

FIG. 8 is a flow chart illustrating one example of processes implementedby first device 400, terminal 450, and base station (or AP) 470illustrated in FIG. 4 .

First, as 801 in FIG. 8 illustrates, first device 400 in FIG. 4transmits a modulated signal having the frame configuration illustratedin FIG. 6 .

Then, as 802 in FIG. 8 illustrates, the modulated signal transmitted byfirst device 400 in FIG. 4 is received, and terminal 450 in FIG. 4performs terminal location or position estimation.

Likewise, as 803 in FIG. 8 illustrates, the modulated signal transmittedby first device 400 in FIG. 4 is received, and terminal 450 in FIG. 4knows the SSID of the base station to be accessed by the terminal.

Then, as 804 in FIG. 8 illustrates, terminal 450 in FIG. 4 transmits, tobase station (or AP) 470 in FIG. 4 , a modulated signal including dataincluding information related to an access destination for obtaininginformation, such as a map, using, for example, radio waves.

As 805 in FIG. 8 illustrates, base station (or AP) 470 receives themodulated signal transmitted by terminal 450, obtains the information onthe access destination, accesses the desired access destination andobtains desired information, such as a map, over a network.

Then, as 806 in FIG. 8 illustrates, base station (or AP) 470 in FIG. 4transmits a modulated signal including desired information, such as theobtained map, to terminal 450 using, for example, radio waves.

As 807 in FIG. 8 illustrates, terminal 450 receives the modulated signaltransmitted by base station (or AP) 470 and obtains (for example) themap. Terminal 450 displays a screen such as the one illustrated in FIG.5 , based on information on (for example) the map and the location orposition of the terminal already obtained.

Next, an example of operations performed when a plurality of firstdevices 400 and base station (or AP) 470 are disposed in the locationillustrated in FIG. 5

Similar to FIG. 5 , FIG. 9 illustrates a map of a given location.

As described with reference to FIG. 5 , FIG. 9 is a map of the thirdfloor of a building. Each of A-1, A-2, A-3, A-4, A-21, A-22, A-23, andA-24 indicates a position of a parking space for an automobile, and B-1and B-2 indicate elevators.

The position of circle 901-1 in FIG. 9 indicates the location of a firstdevice having the same configuration as device 100 illustrated in FIG. 4. A first device having the same configuration as device 100 in FIG. 4at the position of 901-1 is referred to as “first device #1”. The firstdevice #1 holds and transmits, as information related to a location orinformation related to a position, information labeled “A-1”.

The position of circle 901-2 in FIG. 9 indicates the location of a firstdevice having the same configuration as device 100 illustrated in FIG. 4. A first device having the same configuration as device 100 in FIG. 4and located at the position of 901-2 is referred to as “first device#2”. The first device #2 holds and transmits, as information related toa location or information related to a position, information labeled“A-2”.

The position of circle 901-3 in FIG. 9 indicates the location of a firstdevice having the same configuration as device 100 illustrated in FIG. 4. A first device having the same configuration as device 100 in FIG. 4and located at the position of 901-3 is referred to as “first device#3”. The first device #3 holds and transmits, as information related toa location or information related to a position, information labeled“A-3”.

The position of circle 901-4 in FIG. 9 indicates the location of a firstdevice having the same configuration as device 100 illustrated in FIG. 4. A first device having the same configuration as device 100 in FIG. 4and located at the position of 901-4 is referred to as “first device#4”. The first device #4 holds and transmits, as information related toa location or information related to a position, information labeled“A-4”.

The position of circle 901-21 in FIG. 9 indicates the location of afirst device having the same configuration as device 100 illustrated inFIG. 4 . A first device having the same configuration as device 100 inFIG. 4 and located at the position of 901-21 is referred to as “firstdevice #21”. The first device #21 holds and transmits, as informationrelated to a location or information related to a position, informationlabeled “A-21”.

The position of circle 901-22 in FIG. 9 indicates the location of afirst device having the same configuration as device 100 illustrated inFIG. 4 . A first device having the same configuration as device 100 inFIG. 4 and located at the position of 901-22 is referred to as “firstdevice #22”. The first device #22 holds and transmits, as informationrelated to a location or information related to a position, informationlabeled “A-22”.

The position of circle 901-23 in FIG. 9 indicates the location of afirst device having the same configuration as device 100 illustrated inFIG. 4 . A first device having the same configuration as device 100 inFIG. 4 and located at the position of 901-23 is referred to as “firstdevice #23”. The first device #23 holds and transmits, as informationrelated to a location or information related to a position, informationlabeled “A-23”.

The position of circle 901-24 in FIG. 9 indicates the location of afirst device having the same configuration as first device 400illustrated in FIG. 4 . A first device having the same configuration asfirst device 400 in FIG. 4 and located at the position of 901-24 isreferred to as “first device #24”. The first device #24 holds andtransmits, as information related to a location or information relatedto a position, information labeled “A-24”. The position of double circle902 in FIG. 9 indicates the location of a base station (or AP) havingthe same configuration as base station 470 illustrated in FIG. 4 . Here,the SSID of a base station (or AP) having the same configuration as basestation 470 in FIG. 4 and located at the position of 902 is “abcdef”.

When the terminals located around the positions illustrated in the mapin FIG. 9 communicate wirelessly, the terminals may access a basestation (or AP) having the same configuration as base station 470 inFIG. 4 and located at position 902 in FIG. 9 . Accordingly, the firstdevice #1 located at 901-1 in FIG. 9 transmits “abcdef” as informationon an SSID (see 401-1 in FIG. 4 ). Similarly, the first device #2located at 901-2 in FIG. 9 transmits “abcdef” as information on an SSID(see 400-1 in FIG. 4 ).

The first device #3 located at 901-3 in FIG. 9 transmits “abcdef” asinformation on an SSID (see 401-1 in FIG. 4 ).

The first device #4 located at 901-4 in FIG. 9 transmits “abcdef” asinformation on an SSID (see 401-1 in FIG. 4 ).

The first device #21 located at 901-21 in FIG. 9 transmits “abcdef” asinformation on an SSID (see 401-1 in FIG. 4 ).

The first device #22 located at 901-22 in FIG. 9 transmits “abcdef” asinformation on an SSID (see 401-1 in FIG. 4 ).

The first device #23 located at 901-23 in FIG. 9 transmits “abcdef” asinformation on an SSID (see 401-1 in FIG. 4 ).

The first device #24 located at 901-24 in FIG. 9 transmits “abcdef” asinformation on an SSID (see 401-1 in FIG. 4 ).

Next, a specific example of operations will be given.

Assume a terminal having the same configuration as terminal 450 in FIG.4 is positioned at 903-1 in FIG. 9 . The terminal receives a modulatedsignal transmitted by the first device #4 positioned at 901-4 in FIG. 9, and receives position information referred to as “A-4”. Moreover, theterminal obtains information on the SSID “abcdef”, and as a result, theterminal accesses a base station (or AP) that has the same configurationas base station 470 in FIG. 4 and is positioned at 902 in FIG. 9 ,whereby the terminal obtains information, such as a map, from the basestation (or AP) that has the same configuration as base station 470 inFIG. 4 and is positioned at 902 in FIG. 9 . Then, the terminal displaysmap information and position information (see FIG. 5 ; however, FIG. 5is only one, non-limiting example).

Assume a terminal having the same configuration as terminal 450 in FIG.4 is positioned at 903-2 in FIG. 9 . The terminal receives a modulatedsignal transmitted by the first device #22 positioned at 901-22 in FIG.9 , and receives position information referred to as “A-22”. Moreover,the terminal obtains information on the SSID “abcdef”, and as a result,the terminal accesses a base station (or AP) that has the sameconfiguration as base station 470 in FIG. 4 and is positioned at 902 inFIG. 9 , whereby the terminal obtains information, such as a map, fromthe base station (or AP) that has the same configuration as base station470 in FIG. 4 and is positioned at 902 in FIG. 9 . Then, the terminaldisplays map information and position information (see FIG. 5 ; however,FIG. 5 is only one, non-limiting example).

Note that the terminal stores a map (surrounding information) andposition information, such as those illustrated in FIG. 5 , in storageincluded in the terminal, and when the user of the terminal needs it,may make more use of the map (surrounding information) and positioninformation by reading the stored information.

As described above, since the first device transmits the modulatedsignal via visible light, a terminal capable of receiving the modulatedsignal is limited to being located within a region capable of receivingthe signal light from the position of the first device. Accordingly, bythe terminal obtaining the location or position information transmittedby the first device, the terminal can achieve an advantageous effectwhereby it is possible to easily (i.e., without having to performcomplicated signal processing) obtain accurate position information.Moreover, when the first device is disposed in a place where receptionof satellite radio waves from a GPS satellite is difficult, it ispossible to achieve an advantageous effect whereby it is possible forthe terminal to securely obtain accurate position information even inlocations in which reception of radio waves from a GPS satellite isdifficult, by the terminal receiving the modulated signal transmitted bythe first device.

Furthermore, an advantageous effect is achieved in which, based oninformation on the SSID transmitted by the first device, the terminalconnects to the base station (or AP) and obtains information to securelyretrieve information. This is because, when information from a visiblelight modulated signal is obtained, since it is visible light, the usercan easily recognize the first device transmitting the modulated signal,making it possible for the user to determine whether the source ofinformation is secure or not.

For example, when an SSID is obtained from a modulated signaltransmitted by a wireless LAN over radio waves, it is difficult for theuser to determine which device transmitted the radio waves. Accordingly,from the viewpoint of ensuring information security, obtaining the SSIDvia visible light communication is more suitable.

Note that a plurality of input signals may further be in radio device453 in terminal 450 in FIG. 4 . For example, a control signal forcontrolling radio device 453 may be in radio device 453, and informationtransmitted by the base station may be in radio device 453 as inputsignals. Here, based on the control signal, operations for the start ofcommunication by radio device 453 are conceivable as one example. Asdescribed above, the configuration of the first device is not limited tothe configuration of first device 400 in FIG. 4 , moreover theconfiguration of the terminal is not limited to the configuration ofterminal 450 in FIG. 4 , and moreover the device to which base station470 connects is not limited to the configuration illustrated in FIG. 4 .

Moreover, although only one base station (or AP) is exemplified in theconfiguration illustrated in FIG. 4 , a plurality of (secure) basestations (or APs) accessible by the terminal may be included. Here, thesymbol related to an SSID transmitted by first device 400 in FIG. 4 mayinclude information indicating the SSIDs of the plurality of basestations (or APs). Terminal 450 in FIG. 4 may select a base station (orAP) to wirelessly connect to based on the information on the SSIDs ofthe base stations (or connect to the plurality of base stations (orAPs)).

For example, assume there are three base stations (or APs). The threebase stations are named base station #A, base station #B, and basestation #C. The SSID of base station #A is “abcdef”, the SSID of basestation #B is “ghijk”, and the SSID of base station #C is “pqrstu”. Insuch cases, symbol 600-1 related to an SSID in the frame configurationillustrated in FIG. 6 of the modulated signal transmitted by the firstdevice includes information related to the SSID “abcdef” of base station#A, the SSID “ghijk” of base station #B, and the SSID “pqrstu” of basestation #C. Terminal 450 in FIG. 4 receives symbol 600-1 related to anSSID, and based on the SSID “abcdef” of base station #A, the SSID“ghijk” of base station #B, and the SSID “pqrstu” of base station #C,selects a base station (or AP) to wirelessly connect to.

Embodiment 4

FIG. 10 illustrates one example of a configuration of a communicationsystem according to this embodiment. The communication systemillustrated in FIG. 10 includes, for example: device 1000 including anLED light source, lamp, light source, and/or light that emits visiblelight; terminal 1050; and, for example, base station 470 thatcommunicates with terminal 1050. Device 1000 in FIG. 10 includes, forexample, an LED lamp, light source, and/or light that emits visiblelight. Note that device 1000 is referred to as a “second device” in thisembodiment. In second device 1000 in FIG. 10 , elements that operate thesame as in first device 100 in FIG. 1 share like reference marks.

In terminal 1050 in FIG. 10 , components that operate the same asterminal 150 in FIG. 1 share like reference marks.

Note that communication between radio device 453 and base station 470 inFIG. 10 is performed using, for example, radio waves.

In second device 1000 in FIG. 10 , transmitter 102 receives inputs ofinformation 1001-1 related to an SSID, information 1001-2 related to anencryption key, and data 1002, and based on these input signals,generates a (optical) modulated signal, and outputs modulated signal103. For example, modulated signal 103 is transmitted from light source104.

Next, information 1001-1 related to an SSID and information 1001-2related to an encryption key will be described.

First, information 1001-1 related to an SSID will be described.

Information 1001-1 related to an SSID is information indicating the SSIDof base station (or AP) 470 in FIG. 10 . Note that, in this example,base station (or AP) 470 transmits modulated signals over radio waves,and receives radio wave modulated signals. In other words, second device1000 can provide access to base station 470, which is a secure accessdestination for the terminal. With this, terminal 1050 in FIG. 10 canachieve the advantageous effect of being able to securely obtaininformation from base station (or AP) 470. On the other hand, device1000 can restrict the terminals that access base station 470 toterminals in a space in which it is possible to receive optical signalstransmitted (emitted) by device 1000. Note that when terminal 1050receives an optical signal transmitted via a predetermined scheme, itmay be determined that the notified SSID is the SSID of a secure basestation, and, alternatively, processing for determining whether the SSIDis secure or not may be performed. For example, device 1000 may transmita predetermined identifier in an optical signal, and the terminal maydetermine whether the notified SSID is the SSID of a secure base stationor not based on the received identifier.

Note that although FIG. 10 only illustrates base station (or AP) 470,for example, when there is a base station (or AP) other than basestation (or AP) 470, terminal 1050 in FIG. 10 accesses base station (orAP) 470 to obtain information.

Information 1001-2 related to an encryption key is information relatedto an encryption key required for terminal 1050 in FIG. 10 to establishcommunication with base station (or AP) 470 in FIG. 10 . Encryptedcommunication is possible between terminal 1050 in FIG. 10 and basestation (or AP) 470 as a result of terminal 1050 in FIG. 10 obtainingthis information from second device 1000 in FIG. 10 .

Terminal 1050 in FIG. 10 receives the modulated signal transmitted bysecond device 1000. Note that in terminal 1050 in FIG. 10 , componentsthat operate the same as terminal 150 in FIG. 1 and terminal 450 in FIG.4 share like reference marks.

Light receiver 151 included in terminal 1050, examples of which includean image sensor such as a CMOS or organic CMOS image sensor, receivesthe modulated signal transmitted by second device 1000. Receiver 153receives an input of reception signal 152 received by light receiver151, performs processing such as demodulation and error correctiondecoding on the reception signal, and outputs reception data 154.

Data analyzer 155 receives an input of reception data 154, and outputs,based on the reception data, for example, information 1051 on the SSIDof the base station (470) to be connected to, and information 1052 onthe encryption key for communication with the base station (470) to beconnected to. For example, in a wireless local area network (LAN),examples of encryption schemes include wired equivalent privacy (WEP),Wi-Fi™ protected access (WPA), and Wi-Fi protected access 2 (WPA2)(pre-shared key (PSK) mode, extended authentication protocol (EAP)mode). However, the encryption method is not limited to these examples.

Display 157 receives inputs of information 1051 on the SSID andinformation 1052 on the encryption key, and, for example, displays theSSID of the communication partner to be accessed by radio device 453included in the terminal, and the encryption key (this display isreferred to as a “first display” in this embodiment).

For example, after the first display, radio device 453 included interminal 1050 in FIG. 10 receives inputs of information 1051 on the SSIDand information 1052 on the encryption key, and establishes a connectionwith base station (or AP) 470 (for example, the connection uses radiowaves). Here, when base station (or AP) 470 also communicates with radiodevice 453 in terminal 1050 in FIG. 10 , base station (or AP) 470transmits a modulated signal using, for example, radio waves.

Thereafter, radio device 453 included in terminal 1050 in FIG. 10receives inputs of data 1053 and control signal 1054, demodulates data1053 in accordance with control signal 1054, and transmits a modulatedsignal as radio waves.

Then, for example, base station (or AP) 470 transmits data to thenetwork (471) and receives data (472) from the network. Thereafter, forexample, base station (or AP) 470 transmits, to terminal 1050 in FIG. 10, a modulated signal as radio waves.

Radio device 453 included in terminal 1050 in FIG. 10 performsprocessing such as demodulation and error correction decoding on themodulated signal received as radio waves to obtain reception data 1056.Display 157 displays a display based on reception data 1056.

FIG. 11 illustrates one example of a configuration of a frame of amodulated signal transmitted by second device 1000 in FIG. 10 . In FIG.11 , time is represented on the horizontal axis, and symbols that arethe same as in FIG. 2 and FIG. 6 share like reference marks.Accordingly, repeated description thereof will be omitted.

Symbol 600-1 related to an SSID is a symbol for transmitting information1001-1 related to an SSID in FIG. 10 , and symbol 1101 related to anencryption key is a symbol for transmitting information 1001-2 relatedto an encryption key in FIG. 10 . Data symbol 1102 is a symbol fortransmitting data 1002.

The second device transmits preamble 201, control information symbol202, symbol 600-1 related to an SSID, symbol 1101 related to anencryption key, and data symbol 1102. Note that second device 1000 inFIG. 10 may transmit a frame including symbols other than the symbolsillustrated in FIG. 11 . Moreover, the frame configuration, includingthe order in which the symbols are transmitted, is not limited to theconfiguration illustrated in FIG. 11 .

FIG. 12 illustrates one example of a configuration of a frame of amodulated signal transmitted by radio device 453 included in terminal1050 in FIG. 10 . In FIG. 12 , time is represented on the horizontalaxis. As illustrated in FIG. 12 , radio device 453 included in terminal1050 in FIG. 10 transmits, for example, preamble 1201, and thentransmits control information symbol 1202 and information symbol 1203.

Here, preamble 1201 is a symbol used for base station (or AP) 470 thatreceives the modulated signal transmitted by radio device 453 interminal 1050 in FIG. 10 to perform, for example, signal detection,temporal synchronization, frame synchronization, frequencysynchronization, and frequency offset estimation.

Control information symbol 1202 includes data such as informationrelated to the error correction encoding scheme method and/ordemodulation scheme used in the generation of the modulated signal,information related to frame configuration, and information related tothe transmission method used, and base station (or AP) 470, for example,demodulates the modulated signal based on the information included incontrol information symbol 1202.

Information symbol 1203 is a symbol for radio device 453 included interminal 1050 in FIG. 10 to transmit data.

Note that radio device 453 included in terminal 1050 in FIG. 10 maytransmit a frame including symbols other than the symbols illustrated inFIG. 12 (for example, a frame including a pilot symbol (referencesymbol) midway through the information symbol). Moreover, the frameconfiguration, including the order in which the symbols are transmitted,is not limited to the configuration illustrated in FIG. 12 . In FIG. 12, a plurality of symbols may be present along the frequency axis, thatis to say, symbols may be present on a plurality of frequencies (aplurality of carriers).

Note that in Embodiment 3, when radio device 453 included in terminal1050 in FIG. 4 transmits a modulated signal, the frame configurationillustrated in FIG. 12 may be used.

FIG. 7 illustrates one example of a configuration of a frame of amodulated signal transmitted by base station 470 in FIG. 10 . In FIG. 7, time is represented on the horizontal axis. As illustrated in FIG. 7 ,base station 470 transmits, for example, preamble 701, and thentransmits control information symbol 702 and information symbol 703.

Here, preamble 701 is a symbol for radio device 453 included in terminal1050 in FIG. 10 , which receives the modulated signal transmitted bybase station 470, to perform, for example, signal detection, temporalsynchronization, frame synchronization, frequency synchronization,and/or frequency offset estimation.

Control information symbol 702 includes data such as information relatedto the error correction encoding scheme method and/or demodulationscheme used in the generation of the modulated signal, informationrelated to frame configuration, and information related to thetransmission method used, and radio device 453 included in terminal 1050in FIG. 10 , for example, demodulates the modulated signal based on theinformation included in this symbol.

Information symbol 703 is a symbol for base station (or AP) 470 in FIG.10 to transmit data.

Note that base station (or AP) 470 in FIG. 10 may transmit a frameincluding symbols other than the symbols illustrated in FIG. 7 (forexample, a frame including a pilot symbol (reference symbol) midwaythrough the information symbol). Moreover, the frame configuration,including the order in which the symbols are transmitted, is not limitedto the configuration illustrated in FIG. 7 . In FIG. 7 , a plurality ofsymbols may be present along the frequency axis, that is to say, symbolsmay be present on a plurality of frequencies (a plurality of carriers).

Moreover, for example, a modulated signal that has the frameconfiguration illustrated in FIG. 11 and is transmitted by second device1000 being transmitted at a regular timing, e.g., repeatedly transmittedis conceivable. This makes it possible for a plurality of terminals toimplement the operations described above.

FIG. 13 is a flow chart illustrating one example of processesimplemented by second device 1000, terminal 1050, and base station (orAP) 470 in FIG. 10 .

First, as 1301 in FIG. 13 illustrates, second device 1000 in FIG. 10transmits a modulated signal having the frame configuration illustratedin FIG. 11 .

Likewise, as 1302 in FIG. 13 illustrates, the modulated signaltransmitted by second device 1000 in FIG. 10 is received, and terminal1050 in FIG. 10 obtains the SSID of the base station to be accessed byterminal 1050. Likewise, as 1303 in FIG. 13 illustrates, terminal 1050in FIG. 10 obtains an encryption key to be used for communicating withbase station 470 to be accessed by the terminal.

Terminal 1050 in FIG. 10 requests connection with base station 470 inFIG. 10 over radio waves (1304).

As 1305 in FIG. 13 illustrates, terminal 1050 in FIG. 10 completes theconnection with base station 470 in FIG. 10 upon receiving a responsefrom base station 470 in FIG. 10 .

As 1306 in FIG. 13 illustrates, terminal 1050 in FIG. 10 transmitsinformation on the connection destination to base station 470 in FIG. 10using radio waves.

Then, as 1307 in FIG. 13 illustrates, base station 470 in FIG. 10obtains information to be transmitted to terminal 1050 in FIG. 10 fromthe network.

As 1308 in FIG. 13 illustrates, base station 470 in FIG. 10 transmitsthe obtained information to terminal 1050 in FIG. 10 using radio waves,and terminal 1050 in FIG. 10 obtains the information.

For example, when necessary, terminal 1050 in FIG. 10 obtains requiredinformation from the network via base station 470 in FIG. 10 .

As described above, based on the SSID information and the encryption keyinformation transmitted from the second device, the terminal connects tothe base station (or AP) and obtains information, whereby anadvantageous effect that it is possible to securely obtain informationvia the base station (or AP) whose security has been authenticated canbe achieved. This is because, when information from a visible lightmodulated signal is obtained, since it is visible light, the user caneasily determine whether the source of information is secure or not.

For example, when an SSID is obtained from a modulated signaltransmitted by a wireless LAN over radio waves, it is difficult for theuser to determine which device transmitted the radio waves. Accordingly,from the viewpoint of ensuring information security, obtaining the SSIDvia visible light communication is more suitable.

Note that in this embodiment, the second device is exemplified astransmitting encryption key information, but, for example, when the basestation (or AP) does not perform encrypted communication using anencryption key, the second device can transmit only the informationrelated to an SSID without transmitting the encryption key information,that is, the second device may be implemented without the configurationrelated to an encryption key.

Moreover, the configuration of the second device is not limited to theconfiguration illustrated in FIG. 10 , the configuration of the terminalis not limited to the configuration illustrated in FIG. 10 , and theconfiguration of the connection destination of the base station is notlimited to the configuration illustrated in FIG. 10 .

Although in this embodiment, only one base station (or AP) isexemplified in the configuration illustrated in FIG. 10 , a plurality of(secure) base stations (or APs) accessible by the terminal may beincluded (note that these base stations and the terminal transmit andreceive modulated signals using radio waves). Here, the symbol relatedto an SSID transmitted by second device 1000 in FIG. 10 may includeinformation indicating the SSIDs of the plurality of base stations (orAPs). Moreover, the symbol related to an encryption key transmitted bysecond device 1000 in FIG. 10 may include encryption key informationused to connect to the plurality of base stations (or APs). Terminal1050 in FIG. 10 may select a base station (or AP) to wirelessly connectto based on the information on the SSIDs of the base stations and theencryption key information (or connect to the plurality of base stations(or APs)).

For example, assume there are three base stations (or APs). The threebase stations are named base station #A, base station #B, and basestation #C. The SSID of base station #A is “abcdef”, the SSID of basestation #B is “ghijk”, and the SSID of base station #C is “pqrstu”, theencryption key for connecting with base station #A is “123”, theencryption key for connecting with base station #B is “456”, and theencryption key for connecting with base station #C is “789”.

In such cases, symbol 600-1 related to an SSID in the frameconfiguration illustrated in FIG. 11 of the modulated signal transmittedby the second device includes information related to the SSID “abcdef”of base station #A, the SSID “ghijk” of base station #B, and the SSID“pqrstu” of base station #C. The symbol 1101 related to an encryptionkey having the frame configuration illustrated in FIG. 11 includesinformation related to the encryption key “123” for connecting with basestation #A, the encryption key “456” for connecting with base station#B, and the encryption key “789” for connecting with base station #C.

Terminal 1050 in FIG. 10 receives symbol 600-1 related to an SSID andthus obtains the SSID “abcdef” of base station #A, the SSID “ghijk” ofbase station #B, and the SSID “pqrstu” of base station #C, receivessymbol 1101 related to an encryption key and thus obtains the encryptionkey “123” for connecting with base station #A, the encryption key “456”for connecting with base station #B, and the encryption key “789” forconnecting with base station #C. Then, based on this information,terminal 1050 in FIG. 10 selects a base station (or AP) to wirelesslyconnect to (for example, via radio waves), and connects to the selectedbase station (or AP).

As described in this embodiment, as a result of the terminal settingwhich base station to access, utilizing a light source, exemplified hereas an LED light source, a mode for making a special setting forprocesses for establishing a wireless connection between the terminaland base station in the modulated signal for connection over radio wavesthat is transmitted by the terminal is not required, and a mode formaking a special setting for processes for establishing a wirelessconnection between the terminal and base station in the modulated signalfor connection over radio waves that is transmitted by the base stationis not required, whereby an advantageous effect that wirelesscommunication data transmission efficiency improves can be achieved.

As described above, the encryption key may be an encryption key for anSSID on a wireless LAN, may be an encryption key for restricting theform of connection used, the form of service used, and/or theconnectivity range of the network (in other words, any encryption keythat is restrictive is sufficient).

Embodiment 5 (SSID and Password Separation)

FIG. 14 illustrates one example of configurations according to thisembodiment of: devices including, for example, an LED light source,lamp, light source, and/or light that emits visible light; a terminal;and, for example, a base station that communicates with the terminal.The communication system in FIG. 14 includes: device 1400A and 1400Beach including, for example, an LED light source, lamp, light source,and/or light that emits visible light; terminal 1050; and, for example,base station 470 that communicates with terminal 1050. Note that device1400A in FIG. 14 is referred to as a “third device” in this embodiment,and device 1400B in FIG. 14 is referred to as a “fourth device” in thisembodiment. Note that in terminal 1050 in FIG. 14 , operations that arethe same as in FIG. 1 and FIG. 10 share like reference marks. Regardingthe base station or AP as well, operations that are the same as in FIG.4 have the same reference marks as in FIG. 4 .

Note that communication between radio device 453 and base station 470 inFIG. 14 is performed using, for example, radio waves.

In third device 1400A in FIG. 14 , transmitter 1404-1 receives inputs ofinformation 1401-1 related to an SSID and data 1402-1, and based onthese input signals, generates a (optical) modulated signal and outputsmodulated signal 1405-1. Modulated signal 1405-1 is transmitted fromlight source 1406-1.

In fourth device 1400B in FIG. 14 , transmitter 1404-2 receives inputsof information 1403-2 related to an encryption key and data 1402-2, andbased on these input signals, generates a (optical) modulated signal andoutputs modulated signal 1405-2. Modulated signal 1405-2 is transmittedfrom light source 1406-2.

Next, information 1401-1 related to an SSID and information 1403-2related to an encryption key will be described.

First, information 1401-1 related to an SSID will be described.

Information 1401-1 related to an SSID is information indicating the SSIDof base station (or AP) 470 in FIG. 14 . In other words, third device1400A can provide access over radio waves to base station 470, which isa secure access destination for the terminal. With this, terminal 1050in FIG. 14 can achieve the advantageous effect of being able to securelyobtain information from base station (or AP) 470.

Note that when terminal 1050 receives an optical signal transmitted viaa predetermined scheme, it may be determined that the notified SSID isthe SSID of a secure base station, and, alternatively, processing fordetermining whether the SSID is secure or not may be performed. Forexample, device 1400A may transmit a predetermined identifier in anoptical signal, and the terminal may determine whether the notified SSIDis the SSID of a secure base station or not based on the receivedidentifier.

Note that although FIG. 14 only illustrates base station (or AP) 470,for example, when there is a base station (or AP) other than basestation (or AP) 470, terminal 1050 in FIG. 14 accesses base station (orAP) 470 to obtain information.

Information 1403-2 related to an encryption key is information relatedto an encryption key required for terminal 1050 in FIG. 14 to establishcommunication with base station (or AP) 470 in FIG. 14 . Encryptedcommunication is possible between terminal 1050 in FIG. 14 and basestation (or AP) 470 as a result of terminal 1050 in FIG. 14 obtainingthis information from fourth device 1400B in FIG. 14 .

Terminal 1050 in FIG. 14 receives the modulated signal transmitted bythird device 1400A.

Light receiver 151 included in terminal 1050, examples of which includean image sensor such as a CMOS or organic CMOS image sensor, receivesthe modulated signal transmitted by third device 1400A. Receiver 153receives an input of reception signal 152 received by light receiver151, performs processing such as demodulation and error correctiondecoding on the reception signal, and outputs reception data 154.

Data analyzer 155 receives an input of reception data 154, and outputs,based on the reception data, for example, information 1051 on the SSIDof the base station (470) to be connected to.

Accordingly, radio device 453 included in terminal 1050 obtainsinformation on the SSID of the base station to be connected to overradio waves by radio device 453, from information 1051 on the SSID.

Next, terminal 1050 in FIG. 14 receives the modulated signal transmittedby fourth device 1400B.

Light receiver 151 included in terminal 1050, examples of which includean image sensor such as a CMOS or organic CMOS image sensor, receivesthe modulated signal transmitted by fourth device 1400B. Receiver 153receives an input of reception signal 152 received by light receiver151, performs processing such as demodulation and error correctiondecoding on the reception signal, and outputs reception data 154.

Data analyzer 155 receives an input of reception data 154, and outputs,based on the reception data, for example, information 1052 on theencryption key for communication with the base station (470) to beconnected to. For example, in a wireless local area network (LAN),examples of encryption schemes include wired equivalent privacy (WEP),Wi-Fi protected access (WPA), and Wi-Fi protected access 2 (WPA2)(pre-shared key (PSK) mode, extended authentication protocol (EAP)mode). However, the encryption method is not limited to these examples.

Accordingly, radio device 453 included in terminal 1050 obtainsencryption key information for the base station to be connected to byradio device 453, from information 1052 on the encryption key forcommunication with the base station (470) to be connected to (forexample, over radio waves).

Display 157 receives inputs of information 1051 on the SSID andinformation 1052 on the encryption key, and, for example, displays theSSID of the communication partner to be accessed by radio device 453included in the terminal, and the encryption key (this display isreferred to as a “first display” in this embodiment).

For example, after the first display, radio device 453 included interminal 1050 in FIG. 14 receives inputs of information 1051 on the SSIDand information 1052 on the encryption key, and establishes a connectionwith base station (or AP) 470 (for example, the connection uses radiowaves). Here, when base station (or AP) 470 also communicates with radiodevice 453 in terminal 1050 in FIG. 14 , base station (or AP) 470transmits a modulated signal using, for example, radio waves.

Thereafter, radio device 453 included in terminal 1050 in FIG. 14receives inputs of data 1053 and control signal 1054, demodulates data1053 in accordance with control signal 1054, and transmits a modulatedsignal as radio waves.

Then, for example, base station (or AP) 470 transmits data to thenetwork (471) and receives data (472) from the network. Thereafter, forexample, base station (or AP) 470 transmits, to terminal 1050 in FIG. 14, a modulated signal as radio waves.

Radio device 453 included in terminal 1050 in FIG. 14 performsprocessing such as demodulation and error correction decoding on thereceived modulated signal to obtain reception data 1056. Display 157displays a display based on reception data 1056.

FIG. 15 illustrates one example of a configuration of a frame of amodulated signal transmitted by third device 1400A in FIG. 14 . In FIG.15 , time is represented on the horizontal axis, and symbols that arethe same as in FIG. 2 , FIG. 6 , and FIG. 11 share like reference marks.Accordingly, repeated description thereof will be omitted.

Symbol 600-1 related to an SSID is a symbol for transmitting information1401-1 related to an SSID in FIG. 14 . Data symbol 1102 is a symbol fortransmitting data 1402-1.

Third device 1400A transmits preamble 201, control information symbol202, symbol 600-1 related to an SSID, and data symbol 1102. Note thatthird device 1400A in FIG. 14 may transmit a frame including symbolsother than the symbols illustrated in FIG. 15 . Moreover, the frameconfiguration, including the order in which the symbols are transmitted,is not limited to the configuration illustrated in FIG. 15 .

FIG. 16 illustrates one example of a configuration of a frame of amodulated signal transmitted by fourth device 1400B in FIG. 14 . In FIG.16 , time is represented on the horizontal axis, and symbols that arethe same as in FIG. 2 and FIG. 11 share like reference marks.Accordingly, repeated description thereof will be omitted.

Symbol 1101 related to an encryption key is a symbol for transmittinginformation 1403-2 related to an encryption key in FIG. 14 . Data symbol1102 is a symbol for transmitting data 1402-2.

Fourth device 1400B transmits preamble 201, control information symbol202, symbol 1101 related to an encryption key, and data symbol 1102.Note that fourth device 1400B in FIG. 14 may transmit a frame includingsymbols other than the symbols illustrated in FIG. 16 . Moreover, theframe configuration, including the order in which the symbols aretransmitted, is not limited to the configuration illustrated in FIG. 16.

FIG. 12 illustrates one example of a configuration of a frame of amodulated signal transmitted by radio device 453 included in terminal1050 in FIG. 14 . In FIG. 12 , time is represented on the horizontalaxis. As illustrated in FIG. 12 , radio device 453 included in terminal1050 in FIG. 14 transmits, for example, preamble 1201, and thentransmits control information symbol 1202 and information symbol 1203.

Here, preamble 1201 is a symbol used for base station (or AP) 470 thatreceives the modulated signal transmitted by radio device 453 interminal 1050 in FIG. 14 to perform, for example, signal detection,temporal synchronization, frame synchronization, frequencysynchronization, and frequency offset estimation.

Control information symbol 1202 includes data such as informationrelated to the error correction encoding scheme method and/ordemodulation scheme used in the generation of the modulated signal,information related to frame configuration, and information related tothe transmission method used, and base station (or AP) 470, for example,demodulates the modulated signal based on the information included incontrol information symbol 1202.

Information symbol 1203 is a symbol for radio device 453 included interminal 1050 in FIG. 14 to transmit data.

Note that radio device 453 included in terminal 1050 in FIG. 14 maytransmit a frame including symbols other than the symbols illustrated inFIG. 12 (for example, a frame including a pilot symbol (referencesymbol) midway through the information symbol). Moreover, the frameconfiguration, including the order in which the symbols are transmitted,is not limited to the configuration illustrated in FIG. 12 . In FIG. 12, a plurality of symbols may be present along the frequency axis, thatis to say, symbols may be present on a plurality of frequencies (aplurality of carriers).

FIG. 7 illustrates one example of a configuration of a frame of amodulated signal transmitted by base station 470 in FIG. 14 . In FIG. 7, time is represented on the horizontal axis. As illustrated in FIG. 7 ,base station 470 transmits, for example, preamble 701, and thentransmits control information symbol 702 and information symbol 703.

Here, preamble 701 is a symbol for radio device 453 included in terminal1050 in FIG. 14 , which receives the modulated signal transmitted bybase station 470, to perform, for example, signal detection, temporalsynchronization, frame synchronization, frequency synchronization,and/or frequency offset estimation.

Control information symbol 702 includes data such as information relatedto the error correction encoding scheme method and/or demodulationscheme used in the generation of the modulated signal, informationrelated to frame configuration, and information related to thetransmission method used, and radio device 453 included in terminal 1050in FIG. 14 , for example, demodulates the modulated signal based on theinformation included in this symbol.

Information symbol 703 is a symbol for base station (or AP) 470 in FIG.14 to transmit data.

Note that base station (or AP) 470 in FIG. 14 may transmit a frameincluding symbols other than the symbols illustrated in FIG. 7 (forexample, a frame including a pilot symbol (reference symbol) midwaythrough the information symbol). Moreover, the frame configuration,including the order in which the symbols are transmitted, is not limitedto the configuration illustrated in FIG. 7 . In FIG. 7 , a plurality ofsymbols may be present along the frequency axis, that is to say, symbolsmay be present on a plurality of frequencies (a plurality of carriers).

Moreover, for example, a modulated signal that has the frameconfiguration illustrated in FIG. 15 and is transmitted by third device1400A being transmitted at a regular timing, e.g., repeatedlytransmitted is conceivable. This makes it possible for a plurality ofterminals to implement the operations described above.

Similarly, a modulated signal that has the frame configurationillustrated in FIG. 16 and is transmitted by fourth device 1400B beingtransmitted at a regular timing, e.g., repeatedly transmitted isconceivable. This makes it possible for a plurality of terminals toimplement the operations described above.

FIG. 17 is a flow chart illustrating a first example of processesimplemented by third device 1400A, fourth device 1400B, terminal 1050,and base station (or AP) 470 in FIG. 14 . Note that in FIG. 17 ,operations that are the same as in FIG. 13 share like reference marks.

First, as 1701 in FIG. 17 illustrates, third device 1400A in FIG. 14transmits a modulated signal having the frame configuration illustratedin FIG. 15 .

As 1702 in FIG. 17 illustrates, the modulated signal transmitted bythird device 1400A in FIG. 14 is received, and terminal 1050 in FIG. 14obtains the SSID of the base station to be accessed by terminal 1050.

Next, as 1703 in FIG. 17 illustrates, fourth device 1400B in FIG. 14transmits a modulated signal having the frame configuration illustratedin FIG. 16 .

As 1704 in FIG. 17 illustrates, the modulated signal transmitted byfourth device 1400B in FIG. 14 is received, and terminal 1050 in FIG. 14obtains an encryption key to be used for communicating with base station470 to be accessed by the terminal.

Terminal 1050 in FIG. 14 requests connection with base station 470 inFIG. 14 over radio waves (1304).

As 1305 in FIG. 17 illustrates, terminal 1050 in FIG. 14 completes theconnection with base station 470 in FIG. 14 upon receiving a responsefrom base station 470 in FIG. 14 .

As 1306 in FIG. 17 illustrates, terminal 1050 in FIG. 14 transmitsinformation on the connection destination to base station 470 in FIG. 14using radio waves.

Then, as 1307 in FIG. 17 illustrates, base station 470 in FIG. 14obtains information to be transmitted to terminal 1050 in FIG. 14 fromthe network.

As 1308 in FIG. 17 illustrates, base station 470 in FIG. 14 transmitsthe obtained information to terminal 1050 in FIG. 14 using radio waves,and terminal 1050 in FIG. 14 obtains the information.

For example, when necessary, terminal 1050 in FIG. 14 obtains requiredinformation from the network via base station 470 in FIG. 14 .

FIG. 18 is a flow chart illustrating a second example of theabove-described processes implemented by third device 1400A, fourthdevice 1400B, terminal 1050, and base station (or AP) 470 in FIG. 14 .Note that in FIG. 18 , operations that are the same as in FIG. 13 sharelike reference marks.

First, as 1801 in FIG. 18 illustrates, fourth device 1400B in FIG. 14transmits a modulated signal having the frame configuration illustratedin FIG. 16 .

As 1802 in FIG. 18 illustrates, the modulated signal transmitted byfourth device 1400B in FIG. 14 is received, and terminal 1050 in FIG. 14obtains an encryption key to be used for communicating with the basestation to be accessed by terminal 1050.

Next, as 1803 in FIG. 18 illustrates, third device 1400A in FIG. 14transmits a modulated signal having the frame configuration illustratedin FIG. 15 .

As 1804 in FIG. 18 illustrates, the modulated signal transmitted bythird device 1400A in FIG. 14 is received, and terminal 1050 in FIG. 14obtains the SSID of base station 470 to be accessed by the terminal.

Terminal 1050 in FIG. 14 requests connection with base station 470 inFIG. 14 over radio waves (1304).

As 1305 in FIG. 18 illustrates, terminal 1050 in FIG. 14 completes theconnection with base station 470 in FIG. 14 upon receiving a responsefrom base station 470 in FIG. 14 .

As 1306 in FIG. 18 illustrates, terminal 1050 in FIG. 14 transmitsinformation on the connection destination to base station 470 in FIG. 14using radio waves.

Then, as 1307 in FIG. 18 illustrates, base station 470 in FIG. 14obtains information to be transmitted to terminal 1050 in FIG. 14 fromthe network.

As 1308 in FIG. 18 illustrates, base station 470 in FIG. 14 transmitsthe obtained information to terminal 1050 in FIG. 14 using radio waves,and terminal 1050 in FIG. 14 obtains the information.

For example, when necessary, terminal 1050 in FIG. 14 obtains requiredinformation from the network via base station 470 in FIG. 14 .

As described above, based on the SSID information and the encryption keyinformation transmitted from the third and fourth devices, the terminalconnects to the base station (or AP) and obtains information, whereby anadvantageous effect that it is possible to securely obtain informationvia the base station (or AP) whose security has been authenticated canbe achieved. This is because, when information from a visible lightmodulated signal is obtained, since it is visible light, the user caneasily determine whether the source of information is secure or not.

For example, when an SSID is obtained from a modulated signaltransmitted by a wireless LAN over radio waves, it is difficult for theuser to determine which device transmitted the radio waves. Accordingly,from the viewpoint of ensuring information security, obtaining the SSIDvia visible light communication is more suitable.

Note that in this embodiment, the fourth device is exemplified astransmitting encryption key information, but, for example, when the basestation (or AP) does not perform encrypted communication using anencryption key, the fourth device can transmit only the informationrelated to an SSID without transmitting the encryption key information,that is, the fourth device may be implemented without the configurationrelated to an encryption key.

Moreover, as described in this embodiment, by separating the device fortransmitting information related to an SSID and the device fortransmitting information related to an encryption key, the terminal canimplement even more secure communication with the base station.

For example, consider the space illustrated in FIG. 19 . As illustratedin FIG. 19 , the space includes area #1 and area #2, and a wall and adoorway between area #1 and area #2. In this example, movement from area#1 to area #2 and movement from area #2 to area #1 is only possiblethrough the doorway.

A base station (or AP), a third device, and a fourth device are disposedin area #1 in FIG. 19 . Only a third device is disposed in area #2.

Moreover, assume that the radio waves transmitted by the base station(or AP) are receivable in either of areas #1 or #2. Here, a terminal inarea #1 in which a fourth device is disposed can communicate with thebase station. Moreover, even when a terminal connected to the basestation in area #1 moves to area #2, communication with the base stationis still possible.

When a terminal connected to the base station in area #1 moves somewhereother than area #1 or area #2, and then returns to either area #1 orarea #2, communication with the base station is possible.

However, a terminal that cannot enter area #1 cannot obtain anencryption key. In such cases, the terminal can only know the SSID ofthe base station (or AP). Here, communication with the base station viaa service that can be accepted with nothing more than knowledge of theSSID may be received by the terminal.

Accordingly, only a terminal that can enter area #1 can communicate withthe base station, and as a result, communication security can beassured. Moreover, this makes it possible to construct a system that canprovide different services for different areas.

Note that when the encryption key for the terminal to communicate withthe base station changes (for example, on a per time interval basis), aprevious encryption key cannot be used to communicate with the basestation. Using such a system makes it possible to provide securecommunication.

As described above, the encryption key may be an encryption key for anSSID on a wireless LAN, may be an encryption key for restricting theform of connection used, the form of service used, and/or theconnectivity range of the network (in other words, any encryption keythat is restrictive is sufficient).

The configurations of the third and fourth devices are not limited tothe configurations illustrated in FIG. 14 , the configuration of theterminal is not limited to the configuration illustrated in FIG. 14 ,and the configuration of the connection destination of the base stationis not limited to the configuration illustrated in FIG. 14 .

In this embodiment, although only one base station (or AP) isexemplified in the configuration illustrated in FIG. 14 , a plurality of(secure) base stations (or APs) accessible by the terminal may beincluded. Here, the symbol related to an SSID transmitted by thirddevice 1400A in FIG. 14 may include information indicating the SSIDs ofthe plurality of base stations (or APs). Moreover, the symbol related toan encryption key transmitted by fourth device 1400B in FIG. 14 mayinclude encryption key information used to connect to the plurality ofbase stations (or APs). Terminal 1050 in FIG. 14 may select a basestation (or AP) to wirelessly connect to based on the encryption keyinformation and the information on the SSIDs of the base stations (orconnect to the plurality of base stations (or APs)).

For example, assume there are three base stations (or APs). The threebase stations are named base station #A, base station #B, and basestation #C. The SSID of base station #A is “abcdef”, the SSID of basestation #B is “ghijk”, and the SSID of base station #C is “pqrstu”, theencryption key for connecting with base station #A is “123”, theencryption key for connecting with base station #B is “456”, and theencryption key for connecting with base station #C is “789”.

In such cases, symbol 600-1 related to an SSID in the frameconfiguration illustrated in FIG. 15 of the modulated signal transmittedby the third device includes information related to the SSID “abcdef” ofbase station #A, the SSID “ghijk” of base station #B, and the SSID“pqrstu” of base station #C. The symbol 1101 related to an encryptionkey having the frame configuration illustrated in FIG. 16 of themodulated signal transmitted by the fourth device includes informationrelated to the encryption key “123” for connecting with base station #A,the encryption key “456” for connecting with base station #B, and theencryption key “789” for connecting with base station #C.

Terminal 1050 in FIG. 14 receives symbol 600-1 related to an SSID andthus obtains the SSID “abcdef” of base station #A, the SSID “ghijk” ofbase station #B, and the SSID “pqrstu” of base station #C, receivessymbol 1101 related to an encryption key and thus obtains the encryptionkey “123” for connecting with base station #A, the encryption key “456”for connecting with base station #B, and the encryption key “789” forconnecting with base station #C. Then, based on this information,terminal 1050 in FIG. 14 selects a base station (or AP) to wirelesslyconnect to (for example, via radio waves), and connects to the selectedbase station (or AP).

As described in this embodiment, as a result of the terminal settingwhich base station to access, utilizing a light source, exemplified hereas an LED light source, a mode for making a special setting forprocesses for establishing a wireless connection between the terminaland base station in the modulated signal for connection over radio wavesthat is transmitted by the terminal is not required, and a mode formaking a special setting for processes for establishing a wirelessconnection between the terminal and base station in the modulated signalfor connection over radio waves that is transmitted by the base stationis not required, whereby an advantageous effect that wirelesscommunication data transmission efficiency improves can be achieved.

Embodiment 6 (Base Station Includes LED)

FIG. 20 illustrates one example of a configuration of a communicationsystem according to this embodiment. The communication systemillustrated in FIG. 20 includes, for example: an LED light source, lamp,light source, and/or light that emits visible light; base station 2000including radio device 2001; and terminal 1050. Note that in FIG. 20 ,operations that are the same as in FIG. 1 and FIG. 10 share likereference marks.

Note that communication between radio device 2001 and radio device 453in FIG. 20 is performed using, for example, radio waves.

Base station (or AP) 2000 in FIG. 20 includes, for example, an LED lamp,light source, and/or light that emits visible light. First, operationsof one or more elements related to the LED lamp, light source, and/orlight that emits visible light will be described.

Transmitter 102 receives inputs of information 1001-1 related to anSSID, information 1001-2 related to an encryption key, and data 1002,and based on these input signals, generates a (optical) modulatedsignal, and outputs modulated signal 103. For example, modulated signal103 is transmitted from light source 104.

Next, information 1001-1 related to an SSID and information 1001-2related to an encryption key will be described.

First, information 1001-1 related to an SSID will be described.

Information 1001-1 related to an SSID is information indicating the SSIDof, for example, radio device 2001 that uses radio waves in base station(or AP) 2000 in FIG. 20 . In other words, an “element related to the LEDlamp, light source, and/or light that emits visible light” can provideaccess to radio device 2001, which is a secure access destination forthe terminal. With this, terminal 1050 in FIG. 20 can achieve theadvantageous effect of being able to securely obtain information fromradio device 2001.

On the other hand, an element related to the LED lamp, light source,and/or light that emits visible light in base station 200 can restrictthe terminals that access radio device 2001 to terminals in a space inwhich reception of the optical signal transmitted (emitted) by theelement related to the LED lamp, light source, and/or light that emitsvisible light in base station 200 is possible. Note that when terminal1050 receives an optical signal transmitted via a predetermined scheme,it may be determined that the notified SSID is the SSID of a secure basestation, and, alternatively, processing for determining whether the SSIDis secure or not may be performed. For example, an element related tothe LED lamp, light source, and/or light that emits visible light inbase station 2000 may transmit a predetermined identifier in an opticalsignal, and the terminal may determine whether the notified SSID is theSSID of a secure base station or not based on the received identifier.

Note that although FIG. 20 only illustrates base station (or AP) 2000,for example, when there is a base station (or AP) other than basestation (or AP) 2000, terminal 1050 in FIG. 20 accesses base station (orAP) 2000 to obtain information.

Information 1001-2 related to an encryption key is information relatedto an encryption key required for terminal 1050 in FIG. 20 to establishcommunication with radio device 2001 in FIG. 20 . Encryptedcommunication is possible between terminal 1050 in FIG. 20 and radiodevice 2001 as a result of terminal 1050 in FIG. 20 obtaining thisinformation from an element related to the LED lamp, light source,and/or light that emits visible light. Terminal 1050 in FIG. 20 receivesthe modulated signal transmitted by an element related to the LED lamp,light source, and/or light that emits visible light in base station 200.

Note that in terminal 1050 in FIG. 20 , components that operate the sameas terminal 150 in FIG. 1 and terminal 1050 in FIG. 10 share likereference marks.

Light receiver 151 included in terminal 1050, examples of which includean image sensor such as a CMOS or organic CMOS image sensor, receivesthe modulated signal transmitted by an element related to the LED lamp,light source, and/or light that emits visible light in base station 200.Receiver 153 receives an input of reception signal 152 received by lightreceiver 151, performs processing such as demodulation and errorcorrection decoding on the reception signal, and outputs reception data154.

Data analyzer 155 receives an input of reception data 154, and outputs,based on the reception data, for example, information 1051 on the SSIDof radio device 2001 in the base station to be connected to, andinformation 1052 on the encryption key for communication with radiodevice 2001 in the base station to be connected to. For example, in awireless local area network (LAN), examples of encryption schemesinclude wired equivalent privacy (WEP), Wi-Fi protected access (WPA),and Wi-Fi protected access 2 (WPA2) (pre-shared key (PSK) mode, extendedauthentication protocol (EAP) mode). However, the encryption method isnot limited to these examples.

Display 157 receives inputs of information 1051 on the SSID andinformation 1052 on the encryption key, and, for example, displays theSSID of the communication partner to be accessed by radio device 453included in the terminal, and the encryption key (this display isreferred to as a “first display” in this embodiment).

For example, after the first display, radio device 453 included interminal 1050 in FIG. 20 receives inputs of information 1051 on the SSIDand information 1052 on the encryption key, and establishes a connectionwith radio device 2001 in base station (or AP) 2000 (for example, theconnection uses radio waves). Here, when radio device 2001 in basestation (or AP) 2000 also communicates with radio device 453 in terminal1050 in FIG. 20 , radio device 2001 in base station (or AP) 2000transmits a modulated signal using, for example, radio waves.

Thereafter, radio device 453 included in terminal 1050 in FIG. 20receives inputs of data 1053 and control signal 1054, demodulates data1053 in accordance with control signal 1054, and transmits a modulatedsignal as radio waves. Then, for example, radio device 2001 in basestation (or AP) 2000 transmits data to the network (471) and receivesdata (472) from the network.

Thereafter, for example, radio device 2001 in base station (or AP) 2000transmits, to terminal 1050 in FIG. 20 , a modulated signal as radiowaves. Radio device 453 included in terminal 1050 in FIG. 20 performsprocessing such as demodulation and error correction decoding on themodulated signal received as radio waves to obtain reception data 1056.Display 157 displays a display based on reception data 1056.

FIG. 11 illustrates one example of a configuration of a frame of amodulated signal transmitted by transmitter 102 and light source 104 inbase station (or AP) 2000 in FIG. 20 . In FIG. 11 , time is representedon the horizontal axis, and symbols that are the same as in FIG. 2 andFIG. 6 share like reference marks. Accordingly, repeated descriptionthereof will be omitted.

Symbol 600-1 related to an SSID is a symbol for transmitting information1001-1 related to an SSID in FIG. 20 , and symbol 1101 related to anencryption key is a symbol for transmitting information 1001-2 relatedto an encryption key in FIG. 20 . Data symbol 1102 is a symbol fortransmitting data 1002.

Transmitter 102 and light source 104 in base station (or AP) 2000transmit preamble 201, control information symbol 202, symbol 600-1related to an SSID, symbol 1101 related to an encryption key, and datasymbol 1102. Note that transmitter 102 and light source 104 in basestation (or AP) 2000 in FIG. 20 may transmit a frame including symbolsother than the symbols illustrated in FIG. 11 . Moreover, the frameconfiguration, including the order in which the symbols are transmitted,is not limited to the configuration illustrated in FIG. 11 .

FIG. 12 illustrates one example of a configuration of a frame of amodulated signal transmitted by radio device 453 included in terminal1050 in FIG. 20 . In FIG. 12 , time is represented on the horizontalaxis. As illustrated in FIG. 12 , radio device 453 included in terminal1050 in FIG. 20 transmits, for example, preamble 1201, and thentransmits control information symbol 1202 and information symbol 1203.

Here, preamble 1201 is a symbol used for radio device 2001 in basestation (or AP) 2000 that receives the modulated signal transmitted byradio device 453 in terminal 1050 in FIG. 20 to perform, for example,signal detection, temporal synchronization, frame synchronization,frequency synchronization, and frequency offset estimation.

Control information symbol 1202 includes data such as informationrelated to the error correction encoding scheme method and/ordemodulation scheme used in the generation of the modulated signal,information related to frame configuration, and information related tothe transmission method used, and radio device 2001 in base station (orAP) 2000, for example, demodulates the modulated signal based on theinformation included in control information symbol 1202.

Information symbol 1203 is a symbol for radio device 453 included interminal 1050 in FIG. 20 to transmit data.

Note that radio device 453 included in terminal 1050 in FIG. 20 maytransmit a frame including symbols other than the symbols illustrated inFIG. 12 (for example, a frame including a pilot symbol (referencesymbol) midway through the information symbol). Moreover, the frameconfiguration, including the order in which the symbols are transmitted,is not limited to the configuration illustrated in FIG. 12 . In FIG. 12, a plurality of symbols may be present along the frequency axis, thatis to say, symbols may be present on a plurality of frequencies (aplurality of carriers).

FIG. 7 illustrates one example of a configuration of a frame of amodulated signal transmitted by radio device 2001 in FIG. 20 . In FIG. 7, time is represented on the horizontal axis. As illustrated in FIG. 7 ,base station 470 transmits, for example, preamble 701, and thentransmits control information symbol 702 and information symbol 703.

Here, preamble 701 is a symbol for radio device 453 included in terminal1050 in FIG. 20 , which receives the modulated signal transmitted byradio device 2001 in FIG. 20 , to perform, for example, signaldetection, temporal synchronization, frame synchronization, frequencysynchronization, and/or frequency offset estimation.

Control information symbol 702 includes data such as information relatedto the error correction encoding scheme method and/or demodulationscheme used in the generation of the modulated signal, informationrelated to frame configuration, and information related to thetransmission method used, and radio device 453 included in terminal 1050in FIG. 20 , for example, demodulates the modulated signal based on theinformation included in the control information symbol.

Information symbol 703 is a symbol for radio device 2001 in FIG. 20 totransmit data.

Note that radio device 2001 included in base station 2000 in FIG. 20 maytransmit a frame including symbols other than the symbols illustrated inFIG. 7 (for example, a frame including a pilot symbol (reference symbol)midway through the information symbol). Moreover, the frameconfiguration, including the order in which the symbols are transmitted,is not limited to the configuration illustrated in FIG. 7 . In FIG. 7 ,a plurality of symbols may be present along the frequency axis, that isto say, symbols may be present on a plurality of frequencies (aplurality of carriers).

Moreover, for example, a modulated signal that has the frameconfiguration illustrated in FIG. 11 and is transmitted by an elementrelated to the LED lamp, light source, and/or light that emits visiblelight in base station 200 being transmitted at a regular timing, e.g.,repeatedly transmitted is conceivable. This makes it possible for aplurality of terminals to implement the operations described above.

FIG. 21 is a flow chart illustrating one example of processesimplemented by an element related to the LED lamp, light source, and/orlight that emits visible light, terminal 1050, and radio device 2001 inthe base station (or AP) in FIG. 20 .

First, as 1301 in FIG. 21 illustrates, an element related to the LEDlamp, light source, and/or light that emits visible light in FIG. 20transmits a modulated signal having the frame configuration illustratedin FIG. 11 .

Then, as 1302 in FIG. 21 illustrates, the modulated signal transmittedby an element related to the LED lamp, light source, and/or light thatemits visible light in FIG. 20 is received, and terminal 1050 in FIG. 20obtains the SSID of the base station to be accessed by terminal 1050.

Likewise, as 1303 in FIG. 21 illustrates, terminal 1050 in FIG. 20obtains an encryption key to be used for communicating with base station470 to be accessed by the terminal.

Terminal 1050 in FIG. 20 requests connection with radio device 2001included in base station 2000 in FIG. 20 over radio waves (1304).

As 1305 in FIG. 21 illustrates, terminal 1050 in FIG. 20 completes theconnection with radio device 2001 included in base station 2000 in FIG.20 upon receiving a response from radio device 2001 included in basestation 2000 in FIG. 20 .

As 1306 in FIG. 21 illustrates, terminal 1050 in FIG. 20 transmitsinformation on the connection destination to radio device 2001 includedin base station 2000 in FIG. 20 using radio waves.

Then, as 1307 in FIG. 21 illustrates, radio device 2001 included in basestation 2000 in FIG. 20 obtains information to be transmitted toterminal 1050 in FIG. 20 from the network.

As 1308 in FIG. 21 illustrates, radio device 2001 included in basestation 2000 in FIG. 20 transmits the obtained information to terminal1050 in FIG. 20 using radio waves, and terminal 1050 in FIG. 20 obtainsthe information.

For example, when necessary, terminal 1050 in FIG. 20 obtains requiredinformation from the network via radio device 2001 included in basestation 2000 in FIG. 20 .

As described above, based on the SSID information and the encryption keyinformation transmitted from an element related to the LED lamp, lightsource, and/or light that emits visible light in the base station, theterminal connects to the base station (or AP) and obtains information,whereby an advantageous effect that it is possible to securely obtaininformation via the base station (or AP) whose security has beenauthenticated can be achieved. This is because, when information from avisible light modulated signal is obtained, since it is visible light,the user can easily determine whether the source of information issecure or not.

For example, when an SSID is obtained from a modulated signaltransmitted by a wireless LAN over radio waves, it is difficult for theuser to determine which device transmitted the radio waves. Accordingly,from the viewpoint of ensuring information security, obtaining the SSIDvia visible light communication is more suitable.

Note that in this embodiment, an element related to the LED lamp, lightsource, and/or light that emits visible light in the base station isexemplified as transmitting encryption key information, but, forexample, when the base station (or AP) does not perform encryptedcommunication using an encryption key, the element related to the LEDlamp, light source, and/or light that emits visible light in the basestation can transmit only the information related to an SSID withouttransmitting the encryption key information, that is, the elementrelated to the LED lamp, light source, and/or light that emits visiblelight in the base station may be implemented without the configurationrelated to an encryption key.

As illustrated in FIG. 20 , the SSID and encryption key for radio device2001 included in base station 2000 may be overwritten. For example, inFIG. 20 , information 1001-1 related to an SSID and information 1001-2related to an encryption key are received as inputs by radio device2001. Radio device 2001 included in base station 2000 overwrites theSSID and encryption key as per the input information 1001-1 related toan SSID and information 1001-2 related to an encryption key. With this,the security of the communication between the terminal and radio device2001 included in base station 2000 is assured (however, in FIG. 20 ,although radio device 2001 included in base station 2000 has a functionof being able to overwrite the SSID and encryption key, radio device2001 included in base station 2000 may have a configuration in whichthis function is not included).

Moreover, the configuration of an element related to the LED lamp, lightsource, and/or light that emits visible light in the base station is notlimited to the configuration illustrated in FIG. 20 , the configurationof the terminal is not limited to the configuration illustrated in FIG.20 , and the configuration of the connection destination of the radiodevice included in the base station is not limited to the configurationillustrated in FIG. 20 . In this embodiment, although only one basestation (or AP) is exemplified in the configuration illustrated in FIG.20 , a plurality of (secure) base stations (or APs) accessible by theterminal may be included (note that the radio devices in these basestations transmit and receive modulated signals using radio waves).Here, the symbol related to an SSID transmitted by an element related tothe LED lamp, light source, and/or light that emits visible light inFIG. 20 may include information indicating the SSIDs of the plurality ofradio devices in the base stations (or APs). Moreover, the symbolrelated to an encryption key transmitted by an element related to theLED lamp, light source, and/or light that emits visible light in FIG. 20may include encryption key information used to connect to the pluralityof radio devices in the base stations (or APs). Terminal 1050 in FIG. 20may select a radio device in a base station (or AP) to wirelesslyconnect to (for example, over radio waves), based on the information onthe SSIDs and encryption key information of the radio stations in thebase stations (or connect to the plurality of radio devices in theplurality of base stations (or APs)).

For example, assume there are three base stations (or APs) that includeradio devices. The radio devices are named radio device #A, radio device#B, and radio device #C. The SSID of radio device #A is “abcdef”, theSSID of radio device #B is “ghijk”, and the SSID of radio device #C is“pqrstu”, the encryption key for connecting with radio device #A is“123”, the encryption key for connecting with radio device #B is “456”,and the encryption key for connecting with radio device #C is “789”.

In such cases, symbol 600-1 related to an SSID in the frameconfiguration illustrated in FIG. 11 of the modulated signal transmittedby an element related to the LED lamp, light source, and/or light thatemits visible light in base station 200 includes information related tothe SSID “abcdef” of radio device #A, the SSID “ghijk” of radio device#B, and the SSID “pqrstu” of radio device #C. The symbol 1101 related toan encryption key having the frame configuration illustrated in FIG. 11includes information related to the encryption key “123” for connectingwith radio device #A, the encryption key “456” for connecting with radiodevice #B, and the encryption key “789” for connecting with radio device#C.

Terminal 1050 in FIG. 20 receives symbol 600-1 related to an SSID andthus obtains the SSID “abcdef” of radio device #A, the SSID “ghijk” ofradio device #B, and the SSID “pqrstu” of radio device #C, receivessymbol 1101 related to an encryption key and thus obtains the encryptionkey “123” for connecting with radio device #A, the encryption key “456”for connecting with radio device #B, and the encryption key “789” forconnecting with radio device #C. Then, based on this information,terminal 1050 in FIG. 20 selects a base station (or AP) to wirelesslyconnect to (for example, via radio waves), and connects to the selectedbase station (or AP).

As described in this embodiment, as a result of the terminal setting aradio device included in a base station to access using a light source,exemplified here as an LED light source, a mode for making a specialsetting for processes for establishing a wireless connection between theterminal and base station in the modulated signal for connection overradio waves that is transmitted by the terminal is not required, and amode for making a special setting for processes for establishing awireless connection between the terminal and base station in themodulated signal for connection over radio waves that is transmitted bythe base station is not required, whereby an advantageous effect thatwireless communication data transmission efficiency improves can beachieved.

As described above, the encryption key may be an encryption key for anSSID on a wireless LAN, may be an encryption key for restricting theform of connection used, the form of service used, and/or theconnectivity range of the network (in other words, any encryption keythat is restrictive is sufficient).

Embodiment 7 (Plural Base Stations; Access Control Performed)

FIG. 22 illustrates one example of a configuration of a communicationsystem according to this embodiment. The communication systemillustrated in FIG. 22 includes, for example: device 1000 including anLED light source, lamp, light source, and/or light that emits visiblelight; terminal 1050; and, for example, base station #1 470-1, basestation #2 470-2, and base station #3 470-3 that communicate withterminal 1050. Note that in FIG. 22 , operations that are the same as inFIG. 1 , FIG. 4 , and FIG. 10 share like reference marks.

Device 1000 in FIG. 22 includes, for example, an LED lamp, light source,and/or light that emits visible light. Note that device 1000 is referredto as a “fifth device” in this embodiment. Note that communicationbetween radio device radio device 453 and base station #1 470-1, betweenradio device 453 and base station #2 470-2, and between radio device 453and base station #3 470-3 in FIG. 22 is performed using, for example,radio waves.

In fifth device 1000 in FIG. 22 , transmitter 102 receives inputs ofinformation 1001-1 related to an SSID, information 1001-2 related to anencryption key, and data 1002, and based on these input signals,generates a (optical) modulated signal, and outputs modulated signal103. For example, modulated signal 103 is transmitted from light source104.

Next, information 1001-1 related to an SSID and information 1001-2related to an encryption key will be described.

First, information 1001-1 related to an SSID will be described.

For example, information 1001-1 related to an SSID is informationindicating the SSID of base station (or AP) 470-1 in FIG. 22 , the SSIDof base station (or AP) 470-2 in FIG. 22 , and the SSID of base station(or AP) 470-3 in FIG. 22 . Note that, in this example, base stations (orAPs) 470-1, 470-2, and 470-3 transmit modulated signals over radiowaves, and receive radio wave modulated signals. In other words, fifthdevice 1000 can provide access to base stations 470-1, 470-2, and 470-3,which are secure access destinations for the terminal. With this,terminal 1050 in FIG. 22 can achieve the advantageous effect of beingable to securely obtain information from base stations (or APs) 470-1,470-2, and 470-3.

On the other hand, device 1000 can restrict the terminals that accessbase stations 470-1, 470-2, and 470-3 to terminals in a space in whichit is possible to receive optical signals transmitted (emitted) bydevice 1000. Note that when terminal 1050 receives an optical signaltransmitted via a predetermined scheme, it may be determined that thenotified SSID is the SSID of a secure base station, and, alternatively,processing for determining whether the SSID is secure or not may beperformed. For example, device 1000 may transmit a predeterminedidentifier in an optical signal, and the terminal may determine whetherthe notified SSID is the SSID of a secure base station or not based onthe received identifier.

Note that the configuration in FIG. 22 illustrates base stations (or AP)470-1, 470-2, and 470-3, but one or more base stations (or APs) otherthan base stations (or AP) 470-1, 470-2, and 470-3 may also be included.

Information 1001-2 related to an encryption key is information relatedto an encryption key required for terminal 1050 in FIG. 22 to establishcommunication with base stations (or AP) 470-1, 470-2, and 470-3 in FIG.22 . Encrypted communication is possible between the terminal and basestation (or AP) 470-1, between the terminal and base station (or AP)470-2, and between the terminal and base station (or AP) 470-3 as aresult of terminal 1050 in FIG. 22 obtaining this information from fifthdevice 1000 in FIG. 22 .

Terminal 1050 in FIG. 22 receives the modulated signal transmitted byfifth device 1000. Note that in terminal 1050 in FIG. 22 , componentsthat operate the same as terminal 150 in FIG. 1 and terminal 450 in FIG.4 share like reference marks.

Light receiver 151 included in terminal 1050, examples of which includean image sensor such as a CMOS or organic CMOS image sensor, receivesthe modulated signal transmitted by fifth device 1000. Receiver 153receives an input of reception signal 152 received by light receiver151, performs processing such as demodulation and error correctiondecoding on the reception signal, and outputs reception data 154.

Data analyzer 155 receives an input of reception data 154, and outputs,based on the reception data, for example, information 1051 on the SSIDsof the base stations (470-1, 470-2, and 470-3) to be connected to, andinformation 1052 on the encryption keys for communication with the basestations (470-1, 470-2, and 470-3) to be connected to. For example, in awireless local area network (LAN), examples of encryption schemesinclude wired equivalent privacy (WEP), Wi-Fi protected access (WPA),and Wi-Fi protected access 2 (WPA2) (pre-shared key (PSK) mode, extendedauthentication protocol (EAP) mode). However, the encryption method isnot limited to these examples.

Display 157 receives inputs of information 1051 on the SSID andinformation 1052 on the encryption key, and, for example, displays theSSID of the communication partner to be accessed by radio device 453included in the terminal, and the encryption key (this display isreferred to as a “first display” in this embodiment).

For example, after the first display, radio device 453 included interminal 1050 in FIG. 22 receives inputs of information 1051 on the SSIDand information 1052 on the encryption key, and establishes a connectionwith any one of base stations (or APs) 470-1, 470-2, and 470-3 (forexample, the connection uses radio waves). Here, when the base stationalso communicates with radio device 453 in terminal 1050 in FIG. 22 ,the base station transmits a modulated signal using, for example, radiowaves.

Thereafter, radio device 453 included in terminal 1050 in FIG. 22receives inputs of data 1053 and control signal 1054, demodulates data1053 in accordance with control signal 1054, and transmits a modulatedsignal as radio waves.

Then, for example, the base station (or AP) connected to transmits datato the network (any one of 471-1, 471-2, and 471-3) and receives data(any one of 472-1, 472-2, and 472-3) from the network. Thereafter, forexample, the base station connected to transmits, to terminal 1050 inFIG. 22 , a modulated signal as radio waves.

Radio device 453 included in terminal 1050 in FIG. 22 performsprocessing such as demodulation and error correction decoding on themodulated signal received as radio waves to obtain reception data 1056.

Display 157 displays a display based on reception data 1056.

Assume, in the case of FIG. 22 , there are three types of frameconfigurations as modulated signals transmitted by fifth device 1000 inFIG. 22 . FIG. 23 illustrates frame #1 2300-1, which is one of the threetypes of frame configurations, FIG. 24 illustrates frame configuration#2 2300-2, which is one of the three types of frame configurations, andFIG. 25 illustrates frame configuration #3 2300-3, which is one of thethree types of frame configurations.

FIG. 23 illustrates one example of the configuration of frame #1 2300-1of a modulated signal transmitted by fifth device 1000 in FIG. 22 . InFIG. 23 , time is represented on the horizontal axis, and symbols thatare the same as in FIG. 2 and FIG. 11 share like reference marks.Accordingly, repeated description thereof will be omitted. Frame #12300-1 in FIG. 23 is a frame for transmitting information on the SSID ofbase station #1 470-1 in FIG. 22 and an encryption key for base station#1 470-1 (an encryption key for accessing base station #1 470-1) in FIG.22 .

Symbol 2301-1 related to an SSID in FIG. 23 is a symbol for transmittinginformation 1001-1 related to an SSID in FIG. 22 . Moreover, symbol2301-1 related to an SSID in FIG. 23 is a symbol for fifth device 1000in FIG. 22 to transmit the SSID of base station #1 470-1 in FIG. 22 .Symbol 2302-1 related to an encryption key in FIG. 23 is a symbol fortransmitting information 1001-2 related to an encryption key in FIG. 22. Moreover, symbol 2302-1 related to an encryption key in FIG. 23 is asymbol for fifth device 1000 in FIG. 22 to transmit an encryption keyfor base station #1 470-1 (an encryption key for accessing base station#1 470-1) in FIG. 22 .

Fifth device 1000 transmits preamble 201, control information symbol202, symbol 2301-1 related to an SSID, symbol 2302-1 related to anencryption key, and data symbol 1102. Note that fifth device 1000 inFIG. 22 may transmit frame #1 2300-1 including symbols other than thesymbols illustrated in FIG. 23 . Moreover, the configuration of frame #12300-1, including the order in which the symbols are transmitted, is notlimited to the configuration illustrated in FIG. 23 .

FIG. 24 illustrates one example of the configuration of frame #2 2300-2of a modulated signal transmitted by fifth device 1000 in FIG. 22 . InFIG. 24 , time is represented on the horizontal axis, and symbols thatare the same as in FIG. 2 and FIG. 11 share like reference marks.Accordingly, repeated description thereof will be omitted. Frame #22300-2 in FIG. 24 is a frame for transmitting information on the SSID ofbase station #2 470-2 in FIG. 22 and an encryption key for base station#2 470-2 (an encryption key for accessing base station #2 470-2) in FIG.22 .

Symbol 2301-2 related to an SSID in FIG. 24 is a symbol for transmittinginformation 1001-1 related to an SSID in FIG. 22 . Moreover, symbol2301-2 related to an SSID in FIG. 24 is a symbol for fifth device 1000in FIG. 22 to transmit the SSID of base station #2 470-2 in FIG. 22 .

Symbol 2302-2 related to an encryption key in FIG. 24 is a symbol fortransmitting information 1001-2 related to an encryption key in FIG. 22. Moreover, symbol 2302-2 related to an encryption key in FIG. 24 is asymbol for fifth device 1000 in FIG. 22 to transmit an encryption keyfor base station #2 470-2 (an encryption key for accessing base station#2 470-2) in FIG. 22 .

Fifth device 1000 transmits preamble 201, control information symbol202, symbol 2301-2 related to an SSID, symbol 2302-2 related to anencryption key, and data symbol 1102. Note that fifth device 1000 inFIG. 22 may transmit frame #2 2300-2 including symbols other than thesymbols illustrated in FIG. 24 . Moreover, the configuration of frame #22300-2, including the order in which the symbols are transmitted, is notlimited to the configuration illustrated in FIG. 24 .

FIG. 25 illustrates one example of the configuration of frame #3 2300-3of a modulated signal transmitted by fifth device 1000 in FIG. 22 . InFIG. 25 , time is represented on the horizontal axis, and symbols thatare the same as in FIG. 2 and FIG. 11 share like reference marks.Accordingly, repeated description thereof will be omitted. Frame #32300-3 in FIG. 25 is a frame for transmitting information on the SSID ofbase station #3 470-3 in FIG. 22 and an encryption key for base station#3 470-3 (an encryption key for accessing base station #3 470-3) in FIG.22 .

FIG. 25 illustrates one example of the configuration of frame #3 2300-3of a modulated signal transmitted by fifth device 1000 in FIG. 22 . InFIG. 25 , time is represented on the horizontal axis, and symbols thatare the same as in FIG. 2 and FIG. 11 share like reference marks.Accordingly, repeated description thereof will be omitted. Frame #32300-3 in FIG. 25 is a frame for transmitting information on the SSID ofbase station #3 470-3 in FIG. 22 and an encryption key for base station#3 470-3 (an encryption key for accessing base station #3 470-3) in FIG.22 .

Symbol 2301-3 related to an SSID in FIG. 25 is a symbol for transmittinginformation 1001-1 related to an SSID in FIG. 22 . Moreover, symbol2301-3 related to an SSID in FIG. 25 is a symbol for fifth device 1000in FIG. 22 to transmit the SSID of base station #3 470-3 in FIG. 22 .

Symbol 2302-3 related to an encryption key in FIG. 25 is a symbol fortransmitting information 1001-2 related to an encryption key in FIG. 22. Moreover, symbol 2302-3 related to an encryption key in FIG. 25 is asymbol for fifth device 1000 in FIG. 22 to transmit an encryption keyfor base station #3 470-3 (an encryption key for accessing base station#3 470-3) in FIG. 22 . Fifth device 1000 transmits preamble 201, controlinformation symbol 202, symbol 2301-3 related to an SSID, symbol 2302-3related to an encryption key, and data symbol 1102. Note that fifthdevice 1000 in FIG. 22 may transmit frame #3 2300-3 including symbolsother than the symbols illustrated in FIG. 25 . Moreover, theconfiguration of frame #3 2300-3, including the order in which thesymbols are transmitted, is not limited to the configuration illustratedin FIG. 25 .

FIG. 26 illustrates an example of a transmission method used by fifthdevice 1000 in FIG. 22 upon transmitting frame #1 2300-1 in FIG. 23 ,frame #2 2300-2 in FIG. 24 , and frame #3 2300-3 in FIG. 25 . In FIG. 26, time is represented on the horizontal axis.

In FIG. 26 , in the frame #1 group transmissions of 2601-1 and 2601-2,one or more of frames #1 2300-1 illustrated in FIG. 23 are transmitted.In the frame #2 group transmissions of 2602-1 and 2602-2, one or more offrames #2 2300-2 in FIG. 24 are transmitted. In the frame #3 grouptransmissions of 2603-1 and 2603-2, one or more of frames #3 2300-3 inFIG. 25 are transmitted.

This will be described in more detail next.

The recitation “in the frame #1 group transmissions of 2601-1 and2601-2, one or more of frames #1 2300-1 illustrated in FIG. 23 aretransmitted” above will be described.

For example, when an image sensor, such as a CMOS or organic CMOS imagesensor is used in light receiver 151, it is possible to process thereception signal in units of frames in moving or still images. Notethat, for example, when a moving picture is labeled as “4K 30 p”, thenumber of pixels of one frame is 3840×2160, and the moving pictureincludes 30 frames per second.

Accordingly, when fifth device 1000 in FIG. 22 transmits a modulatedsignal including frame #1 2300-1 in FIG. 23 , frame #2 2300-2 in FIG. 24, and frame #3 2300-3 in FIG. 25 in a single frame, terminal 1050 inFIG. 22 has difficulty in selecting a base station to access from amongthe plurality of base stations.

In view of this, a frame configuration such as illustrated in FIG. 26 isproposed.

Method 1-1:

Method 1-1 makes the temporal space that frame #1 group transmissionoccupies longer than a frame of a still or moving picture by including aplurality of frames #1 2300-1 illustrated in FIG. 23 , in frame #1 grouptransmissions of 2601-1 and 2601-2.

This method makes it possible for terminal 1050 in FIG. 22 to easilyselect a base station to access from among the plurality of basestations since terminal 1050 in FIG. 22 can prevent the reception of amodulated signal including, in a single frame of a still or movingpicture, frame #1 2300-1 in FIG. 23 , frame #2 2300-2 in FIG. 24 , andframe #3 2300-3 in FIG. 25 , by fifth device 1000.

Method 2-1:

Method 2-1 makes the temporal space that frame #1 2300-1 in FIG. 23occupies longer than a frame of a still or moving picture. For example,symbol 2301-1 related to an SSID in FIG. 23 may include a plurality ofitems of the information on the SSID for base station #1 (theinformation on the SSID for base station #1 is repeatedly included), orsymbol 2302-1 related to an encryption key may include a plurality ofitems of the information on the encryption key for base station #1 (theencryption key for connecting with base station #1) (the information onthe encryption key for base station #1 (the encryption key forconnecting with base station #1) is repeatedly included).

This method makes it possible for terminal 1050 in FIG. 22 to easilyselect a base station to access from among the plurality of basestations since terminal 1050 in FIG. 22 can prevent the reception of amodulated signal including, in a single frame of a still or movingpicture, frame #1 2300-1 in FIG. 23 , frame #2 2300-2 in FIG. 24 , andframe #3 2300-3 in FIG. 25 , by fifth device 1000.

Similarly, frame #2 group transmissions of 2602-1 and 2602-2 may havethe following configurations.

Method 1-2:

Method 1-2 makes the temporal space that frame #2 group transmissionoccupies longer than a frame of a still or moving picture by including aplurality of frames #2 2300-2 illustrated in FIG. 24 , in frame #2 grouptransmissions of 2602-1 and 2602-2.

Method 2-2:

Method 2-2 makes the temporal space that frame #2 2300-2 in FIG. 24occupies longer than a frame of a still or moving picture. For example,symbol 2301-2 related to an SSID in FIG. 24 may include a plurality ofitems of the information on the SSID for base station #2 (theinformation on the SSID for base station #2 is repeatedly included), orsymbol 2302-2 related to an encryption key may include a plurality ofitems of the information on the encryption key for base station #2 (theencryption key for connecting with base station #2) (the information onthe encryption key for base station #2 (the encryption key forconnecting with base station #2) is repeatedly included).

Similarly, frame #3 group transmissions of 2603-1 and 2603-2 may havethe following configurations.

Method 1-3:

Method 1-3 makes the temporal space that frame #3 group transmissionoccupies longer than a frame of a still or moving picture by including aplurality of frames #3 2300-3 illustrated in FIG. 25 , in frame #3 grouptransmissions of 2603-1 and 2603-2.

Method 2-3:

Method 2-3 makes the temporal space that frame #3 2300-3 in FIG. 25occupies longer than a frame of a still or moving picture. For example,symbol 2301-3 related to an SSID in FIG. 25 may include a plurality ofitems of the information on the SSID for base station #3 (theinformation on the SSID for base station #3 is repeatedly included), orsymbol 2302-3 related to an encryption key may include a plurality ofitems of the information on the encryption key for base station #3 (theencryption key for connecting with base station #3) (the information onthe encryption key for base station #3 (the encryption key forconnecting with base station #3) is repeatedly included).

Next, the advantageous effects achieved when fifth device 1000 in FIG.22 transmits a frame, such as those illustrated in FIG. 23 through FIG.26 , will be described.

Consider area 2700 in FIG. 27 . Fifth devices 1000 having theconfiguration illustrated in FIG. 22 are disposed at circles 2701-1,2701-2, 2701-3, 2701-4, 2701-5, 2701-6, 2701-7, 2701-8, 2701-8, 2701-9,and 2701-10. Base station #1 470-1 in FIG. 22 is disposed at doublecircle 2702-1, base station #2 470-2 in FIG. 22 is disposed at doublecircle 2702-2, and base station #3 470-3 in FIG. 22 is disposed atdouble circle 2702-3.

For example, 99 terminals having the configuration of 1050 in FIG. 22are present in the area indicated as 2703.

Here, for example, fifth devices 2701-5 and 2701-10 both transmitinformation on the SSID of base station #3 470-3 and information on theencryption key for access to base station #3 470-3 (since the basestation closest to fifth devices 2701-5 and 2701-10 is base station #3470-3).

In such cases, all of the 99 terminals having the configuration of 1050in FIG. 22 will access base station #3 470-3 in FIG. 22 . This meansthere is a high probability that the terminals having the configurationof 1050 in FIG. 22 will have difficulty accessing base station #3 470-3in FIG. 22 .

Taking this point into consideration, by making it so that the 99terminals having the configuration of 1050 in FIG. 22 access basestation #1 470-1 (2702-1) in FIG. 22 , base station #2 470-2 (2702-2) inFIG. 22 , and base station #3 470-3 (2702-3) in FIG. 22 as evenly aspossible, it is possible to achieve the advantageous effect of areduction in terminals having difficulty accessing a base station, asdescribed above.

In this embodiment, when fifth device 1000 in FIG. 22 transmits a frame,such as those illustrated in FIG. 23 through FIG. 26 , the 99 terminalshaving the configuration of 1050 in FIG. 22 typically access fifthdevice 1000 in FIG. 22 at different timings, so the 99 terminals havingthe configuration of 1050 in FIG. 22 access base station #1 470-1(2702-1) in FIG. 22 , base station #2 470-2 (2702-2) in FIG. 22 , andbase station #3 470-3 (2702-3) in FIG. 22 as evenly as possible.Accordingly, the previously-described advantageous effect of a reductionin terminals having difficulty accessing a base station can be achieved.In other words, it is possible to achieve an advantageous effect thatconcentration of access from a plurality of terminals to any given basestation can be avoided.

Note that although FIG. 26 illustrates an example of a transmissionmethod used upon fifth device 1000 in FIG. 22 transmitting frame #12300-1 in FIG. 23 , frame #2 2300-2 in FIG. 24 , and frame #3 2300-3 inFIG. 25 , the transmission method used upon fifth device 1000 in FIG. 22transmitting frame #1 2300-1 in FIG. 23 , frame #2 2300-2 in FIG. 24 ,and frame #3 2300-3 in FIG. 25 is not limited to this example.

For example, in FIG. 26 , the order of frame #1 group transmission,frame #2 group transmission, and frame #3 group transmission isrepeated, but the order in which frame #1 group transmission, frame #2group transmission, and frame #3 group transmission are transmitted isnot limited to the example given in FIG. 26 . For example, thetransmission of frame group #1, the transmission of frame group #2, andthe transmission of frame group #3 may be temporally randomized, and,alternatively, the order of the transmission of frame group #1, thetransmission of frame group #2, and the transmission of frame group #3may be a regular order different than the example given in FIG. 26 . Itis sufficient so long as fifth device 1000 in FIG. 22 transmits frame #1group, frame #2 group, and frame #3 group. For example, when fifthdevice 1000 temporally randomizes the transmission of frame group #1,the transmission of frame group #2, and the transmission of frame group#3, a random number may be generated at a given timing, and the framegroup specified by that random number may be transmitted at that time.Note that the usage of a random number is merely one non-limitingexample.

Moreover, in FIG. 26 , frame #1 group transmission, frame #2 grouptransmission, and frame #3 group transmission are exemplified as beingperformed consecutively, but these transmissions do not necessarily needto be performed consecutively. For example, in FIG. 26 , there may be atime interval between frame #1 group transmission 2601-1 and frame #2group transmission 2602-2.

In FIG. 26 , the example includes only frame #1 group transmission,frame #2 group transmission, and frame #3 group transmission, but othersymbols and/or frames may be included. Furthermore, in FIG. 26 and FIG.22 , there are three base stations, but the number of base stations isnot limited to this example. As long as there are two or more basestations, they can operate the same as when there are three.Accordingly, for example, when there are N base stations (N is aninteger of 2 or more), when transmission such as that illustrated inFIG. 26 is performed, frame #k group transmission is performed. Notethat k is an integer greater than or equal to 1 and less than or equalto N. Then, in the transmission of frame #k group, there is a symbolrelated to an SSID (information on the SSID of base station #k) and asymbol related to an encryption key (information on an encryption keyfor base station #k).

FIG. 12 illustrates one example of a configuration of a frame of amodulated signal transmitted by radio device 453 included in terminal1050 in FIG. 22 . In FIG. 12 , time is represented on the horizontalaxis. As illustrated in FIG. 12 , radio device 453 included in terminal1050 in FIG. 22 transmits, for example, preamble 1201, and thentransmits control information symbol 1202 and information symbol 1203.

Here, preamble 1201 is a symbol used for base stations (or APs) 470-1,470-2, and 470-3 that receive the modulated signal transmitted by radiodevice 453 in terminal 1050 in FIG. 22 to perform, for example, signaldetection, temporal synchronization, frame synchronization, frequencysynchronization, and frequency offset estimation.

Control information symbol 1202 includes data such as informationrelated to the error correction encoding scheme method and/ordemodulation scheme used in the generation of the modulated signal,information related to frame configuration, and information related tothe transmission method used, and base stations (or APs) 470-1, 470-2,and 470-3, for example, demodulate the modulated signal based on theinformation included in control information symbol 1202.

Information symbol 1203 is a symbol for radio device 453 included interminal 1050 in FIG. 22 to transmit data.

Note that radio device 453 included in terminal 1050 in FIG. 22 maytransmit a frame including symbols other than the symbols illustrated inFIG. 12 (for example, a frame including a pilot symbol (referencesymbol) midway through the information symbol). Moreover, the frameconfiguration, including the order in which the symbols are transmitted,is not limited to the configuration illustrated in FIG. 12 . In FIG. 12, a plurality of symbols may be present along the frequency axis, thatis to say, symbols may be present on a plurality of frequencies (aplurality of carriers).

FIG. 7 illustrates one example of a configuration of a frame of amodulated signal transmitted by base stations 470-1, 470-2, and 470-3 inFIG. 22 . In FIG. 7 , time is represented on the horizontal axis. Asillustrated in FIG. 7 , base stations 470-1, 470-2, and 470-3 transmit,for example, preamble 701, and then transmit control information symbol702 and information symbol 703.

Here, preamble 701 is a symbol for radio device 453 included in terminal1050 in FIG. 22 , which receives the modulated signals transmitted bybase stations 470-1, 470-2, and 470-3, to perform, for example, signaldetection, temporal synchronization, frame synchronization, frequencysynchronization, and/or frequency offset estimation.

Control information symbol 702 includes data such as information relatedto the error correction encoding scheme method and/or demodulationscheme used in the generation of the modulated signal, informationrelated to frame configuration, and information related to thetransmission method used, and radio device 453 included in terminal 1050in FIG. 22 , for example, demodulates the modulated signal based on theinformation included in the control information symbol.

Information symbol 703 is a symbol for base stations (or APs) 470-1,470-2, and 470-3 in FIG. 22 to transmit data.

Note that base stations (or APs) 470-1, 470-2, and 470-3 in FIG. 22 maytransmit a frame including symbols other than the symbols illustrated inFIG. 7 (for example, a frame including a pilot symbol (reference symbol)midway through the information symbol). Moreover, the frameconfiguration, including the order in which the symbols are transmitted,is not limited to the configuration illustrated in FIG. 7 . In FIG. 7 ,a plurality of symbols may be present along the frequency axis, that isto say, symbols may be present on a plurality of frequencies (aplurality of carriers).

FIG. 28 is a flow chart illustrating one example of processesimplemented by fifth device 1000, terminal 1050, and base station #X (orAP #X) in FIG. 22 . Note that X is 1, 2, or 3.

First, as 2801 in FIG. 28 illustrates, fifth device 1000 in FIG. 22transmits a modulated signal having the frame configuration illustratedin FIG. 26 .

Likewise, as 2802 in FIG. 28 illustrates, the modulated signaltransmitted by fifth device 1000 in FIG. 22 is received, and terminal1050 in FIG. 22 selects the base station to be accessed by terminal 1050from among base station #1 470-1, base station #2 470-2, and basestation #3 470-3 in FIG. 22 .

This point will be discussed next. Terminal 1050 in FIG. 22 attempts toaccess a base station, and receives a modulated signal transmitted byfifth device 1000 in FIG. 22 . Here, for example, in one frame of amoving or still picture, any one of frame #1 group transmission, frame#2 group transmission, and frame #3 group transmission in FIG. 26 isobtained. Then, from the obtained information on the base station (forexample, the SSID), terminal 1050 in FIG. 22 determines which of basestation #1 470-1, base station #2 470-2, and base station #3 470-3 inFIG. 22 to access.

For example, terminal 1050 selects the frame group transmission firstreceived from among frame #1 group transmission, frame #2 grouptransmission, and frame #3 group transmission, and determines the basestation to access from the information on the base station from thatframe group transmission (for example, the SSID).

As 2803 in FIG. 28 illustrates, the modulated signal transmitted byfifth device 1000 in FIG. 22 is received, and terminal 1050 in FIG. 22obtains the SSID of base station #X to be accessed by terminal 1050.

Likewise, as 2804 in FIG. 28 illustrates, terminal 1050 in FIG. 22obtains an encryption key to be used for communicating with base station#X to be accessed by the terminal.

Terminal 1050 in FIG. 22 then requests connection with base station #Xover radio waves (2805).

As 2806 in FIG. 28 illustrates, terminal 1050 in FIG. 22 completes theconnection with base station #X upon receiving a response from basestation #X.

As 2807 in FIG. 28 illustrates, terminal 1050 in FIG. 22 transmitsinformation on the connection destination to base station #X using radiowaves.

Then, as 2808 in FIG. 28 illustrates, base station #X obtainsinformation to be transmitted to terminal 1050 in FIG. 22 from thenetwork.

As 2809 in FIG. 28 illustrates, base station #X transmits the obtainedinformation to terminal 1050 in FIG. 22 using radio waves, and terminal1050 in FIG. 22 obtains the information.

For example, when necessary, terminal 1050 in FIG. 22 obtains requiredinformation from the network via base station #X.

As described above, based on the SSID information and the encryption keyinformation transmitted from the fifth device, the terminal connects tothe base station (or AP) and obtains information, whereby anadvantageous effect that it is possible to securely obtain informationvia the base station (or AP) whose security has been authenticated canbe achieved. This is because, when information from a visible lightmodulated signal is obtained, since it is visible light, the user caneasily determine whether the source of information is secure or not.

For example, when an SSID is obtained from a modulated signaltransmitted by a wireless LAN over radio waves, it is difficult for theuser to determine which device transmitted the radio waves. Accordingly,from the viewpoint of ensuring information security, obtaining the SSIDvia visible light communication is more suitable.

Note that in this embodiment, the fifth device is exemplified astransmitting encryption key information, but, for example, when the basestation (or AP) does not perform encrypted communication using anencryption key, the fifth device can transmit only the informationrelated to an SSID without transmitting the encryption key information,that is, the fifth device may be implemented without the configurationrelated to an encryption key.

Moreover, the configuration of the fifth device is not limited to theconfiguration illustrated in FIG. 22 , the configuration of the terminalis not limited to the configuration illustrated in FIG. 22 , and theconfigurations of the connection destination of base stations #1, #2,and #3 are not limited to the configurations illustrated in FIG. 22 .

Accordingly, when a configuration such as the one described in thisembodiment is implemented, when there are a plurality of terminals in agiven area, an advantageous effect of a reduction in terminals havingdifficulty accessing a base station can be achieved.

Note that in FIG. 27 , the frame configurations of the modulated signalstransmitted by the fifth devices disposed at circles 2701-1, 2701-2,2701-3, 2701-4, 2701-5, 2701-6, 2701-7, 2701-8, 2701-8, 2701-9, and2701-10 may all be the same as illustrated in FIG. 26 , the frameconfigurations of the modulated signals transmitted by the fifth devicesmay be mutually different, and two or more of the fifth devices maytransmit modulated signals having the same frame configuration.

Moreover, in this embodiment, the terminal connects to the base stationor access point in a wireless LAN using radio waves, but the device thatthe terminal connects to may be any device that the terminal can connectto using radio waves, and is not limited to a base station or accesspoint in a wireless LAN. For example, the device may be a base stationsuch as a mobile phone, or a relay station. Moreover, in thisembodiment, an example is given in which information on an SSID isincluded in the modulated signal, but the SSID is merely onenon-limiting example. In other words, the information included in themodulated signal may be any information from which a secure base stationto which the terminal may connect to can be identified; the informationis not limited to including an SSID. Moreover, the terminal may be anydevice that has the functions that terminal 1050 in FIG. 22 has, andmay, for example, may be a vehicle itself or be a device includingtransmitting and receiving functions that is included in a vehicle.

Embodiment 7 Summary

As described above, the transmission device according to this embodimentis, for example, device 1000 described above, and includes light source104 and transmitter 102 that that generates a modulated signal based onan input signal and transmits the modulated signal from light source 104as visible light by changing the luminance of light source 104 inaccordance with the modulated signal. The modulated signal includes aplurality of items of information related to service set identifiers(SSIDs) of a plurality of mutually different access points in a wirelesslocal area network (LAN).

Here, the modulated signal may include a plurality of frame groupsrespectively corresponding to the plurality of mutually different accesspoints and each including one or more frames, and each of the one ormore frames included in the plurality of frame groups may include theinformation related to the SSID of the access point corresponding to theframe group including the frame.

Moreover, the time required to transmit one of the plurality of framegroups may be longer than the time required to image one frame of amoving or still image by the reception device that receives themodulated signal.

Alternatively, the modulated signal may include a plurality of framesrespectively corresponding to the plurality of mutually different accesspoints, and each of the plurality of frames may include one or moreitems of the information related to the SSID of the access pointcorresponding to the frame. The time required to transmit one of theplurality of frames may be longer than the time required to image oneframe of a moving or still image by the reception device that receivesthe modulated signal.

Moreover, transmitter 102 may transmit the plurality of frame groupsrespectively corresponding to the plurality of mutually different accesspoints in random order along a time or frequency axis.

Alternatively, transmitter 102 may transmit the plurality of framegroups respectively corresponding to the plurality of mutually differentaccess points in a regular order along a time or frequency axis.

The reception device according to the present embodiment is terminal1050 that, for example, receives modulated signal transmitted as visiblelight from the transmission device. More specifically, the receptiondevice includes: light receiver 151 that receives a modulated signaltransmitted as visible light from a transmission device; data analyzer155 that outputs analysis information by analyzing data based on themodulated signal; and a radio unit configured to, based on the analysisinformation, connect to an access point in a wireless local area network(LAN) using radio waves. For example, the radio unit is radio device453. Here, the modulated signal includes a plurality of items ofinformation related to service set identifiers (SSIDs) of a plurality ofmutually different access points in the wireless LAN. Data analyzer 155selects any one of the plurality of items of the information related tothe SSIDs of the plurality of mutually different access points includedin the modulated signal, and outputs, as the analysis information, theinformation related to the SSID selected. The radio unit connects to,using radio waves, the access point corresponding to the informationrelated to the SSID output from data analyzer 155, from among theplurality of mutually different access points.

Here, the modulated signal may include a plurality of frame groupsrespectively corresponding to the plurality of mutually different accesspoints and each including one or more frames, and each of the one ormore frames included in the plurality of frame groups may include theinformation related to the SSID of the access point corresponding to theframe group including the frame.

The time required to receive one of the plurality of frame groups bylight receiver 151 may be longer than the time required to image oneframe of a moving or still image by light receiver 151.

Alternatively, the modulated signal may include a plurality of framesrespectively corresponding to the plurality of mutually different accesspoints, and each of the plurality of frames may include one or moreitems of the information related to the SSID of the access pointcorresponding to the frame. The time required to receive one of theplurality of frames by light receiver 151 may be longer than the timerequired to image one frame of a moving or still image by light receiver151.

Moreover, light receiver 151 may receive the plurality of frame groupsrespectively corresponding to the plurality of mutually different accesspoints in random order along a time or frequency axis.

Alternatively, light receiver 151 may receive the plurality of framegroups respectively corresponding to the plurality of mutually differentaccess points in a regular order along a time or frequency axis.

The communication system according to the present embodiment includes atransmission device and a plurality of mutually different access pointsin a wireless local area network (LAN). The transmission device is, forexample, device 1000, and the plurality of access points include, forexample, base station #1 470-1, base station #2 470-2, and base station#3 470-3. The transmission device includes: light source 104; andtransmitter 102 that generates a modulated signal based on an inputsignal and transmits the modulated signal from light source 104 asvisible light by changing the luminance of light source 104 inaccordance with the modulated signal. The modulated signal includes aplurality of items of information related to service set identifiers(SSIDs) of the plurality of mutually different access points, and atleast one of the plurality of mutually different access points connects,using radio waves, to a reception device that received the modulatedsignal, and transmits information to the reception device.

Moreover, the transmission method according to the present embodimentincludes: generating a modulated signal based on an input signal; andtransmitting the modulated signal from a light source as visible lightby changing a luminance of the light source in accordance with themodulated signal. The modulated signal includes a plurality of items ofinformation related to service set identifiers (SSIDs) of a plurality ofaccess points on mutually different wireless local area networks (LANs).

The reception method according to the present embodiment includes:receiving a modulated signal transmitted as visible light from atransmission device; outputting analysis information by analyzing databased on the modulated signal; and based on the analysis information,connecting to an access point in a wireless local area network (LAN)using radio waves. Here, the modulated signal includes a plurality ofitems of information related to service set identifiers (SSIDs) of aplurality of mutually different access points in the wireless LAN. Theoutputting of analysis information includes: selecting any one of theplurality of items of the information related to the SSIDs of theplurality of mutually different access points included in the modulatedsignal; and outputting, as the analysis information, the item ofinformation related to the SSID selected. The connecting to the accesspoint in the wireless LAN includes connecting to, using radio waves, theaccess point corresponding to the item of information related to theSSID output via the analyzing, from among the plurality of mutuallydifferent access points.

Moreover, the communication method according to the present embodimentincludes: generating a modulated signal based on an input signal; andtransmitting the modulated signal from a light source as visible lightby changing a luminance of the light source in accordance with themodulated signal. The modulated signal includes a plurality of items ofinformation related to service set identifiers (SSIDs) of a plurality ofmutually different access points in a local area network (LAN). At leastone of the plurality of mutually different access points connects, usingradio waves, to a reception device that received the modulated signal,and transmits information to the reception device.

Supplemental Information 1 for Above Embodiments

Note that at least one of the field programmable gate array (FPGA) andcentral processing unit (CPU) may be configured to be able to downloadall or part of software required for implementing the communicationmethod described in the present disclosure via wireless or wiredcommunication, and moreover may be configured to be able to download allor part of software for receiving updates via wireless or wiredcommunication. The downloaded software may be stored in storage, and thedigital signal processing described in the present disclosure may beimplemented by operating at least one of the FPGA and CPU based on thestored software.

Here, a device including at least one of the FPGA and CPU may beconnected to a telecommunications modem via a wireless or wiredconnection, and the communication method described in the presentdisclosure may be implemented by the device and the telecommunicationsmodem.

For example, a communication device, such as the base station, AP,terminal described in the present specification may include at least oneof an FPGA and a CPU, and may include an interface for obtainingsoftware for operating the at least one of an FPGA and a CPU from anexternal source. Furthermore, the communication device may includestorage for storing software obtained from an external source, and mayimplement the signal processing described in the present disclosure byoperating the FPGA and/or CPU based on the stored software.

The transmission device described in the present specification may beincluded in a first automobile or vehicle, and the reception devicedescribed in the present specification may be included in a secondautomobile or vehicle, and the transmission and receiving of data may beimplemented under such a configuration.

The transmission device or part of the functions of the transmissiondevice described in the present specification may be connected to thefirst automobile or vehicle via an interface, and the reception deviceor part of the functions of the reception device described in thepresent specification may be connected to the second automobile orvehicle via an interface, and the transmission of data may beimplemented via transmission and reception thereby.

The transmission device described in the present specification may beincluded in a first automobile or vehicle, and the transmission andreceiving of data between this transmission device and the receptiondevice described in the present specification may be implemented undersuch a configuration.

The reception device described in the present specification may beincluded in a second automobile or vehicle, and the transmission andreceiving of data between this reception device and the transmissiondevice described in the present specification may be implemented undersuch a configuration.

Furthermore, the transmission device or part of the functions of thetransmission device described in the present specification may beconnected to the first automobile or vehicle via an interface, and thetransmission and receiving of data between this string of transmissiondevices and the reception device described in the present specificationmay be implemented under such a configuration.

The reception device or part of the functions of the reception devicedescribed in the present specification may be connected to the secondautomobile or vehicle via an interface, and the transmission andreceiving of data between this string of reception devices and thetransmission device described in the present specification may beimplemented under such a configuration.

When the automobile or vehicle includes the transmission device or partof the transmission device described in the present specification, orwhen the automobile or vehicle and the transmission device described inthe present specification or part of the functions of the transmissiondevice described in the present specification are connected via aninterface, the light source included in the transmission devicedescribed in the present specification may be a light source included inthe automobile or vehicle.

For example, automobile B100 illustrated in FIG. 29 includes lightsources B101_1, B101_2, B101_3, and B101_4, and one or more of theselight sources may be the light source to be used by the transmissiondevice according to the present specification for transmitting theoptical modulated signal.

Moreover, the function for selecting which light source among theplurality of light sources included in automobile B100 the transmissiondevice according to the present specification uses for transmitting theoptical modulated signal may be included in the transmission device or adevice connected to the transmission device. Moreover, the brightness ofthe light source, the angle of emission of the light source, thepositioning of the light source may be configurable.

When the automobile or vehicle includes the reception device or part ofthe reception device described in the present specification, or when theautomobile or vehicle and the reception device described in the presentspecification or part of the functions of the reception device describedin the present specification are connected via an interface, the lightreceiver included in the reception device described in the presentspecification may be a light receiver included in the automobile orvehicle (for example, an image sensor or photodiode).

For example, automobile B100 illustrated in FIG. 30 includes lightreceivers B201_1, B201_3, B201_4, and B201_5, and one or more of theselight receivers may be the light receiver to be used by the receptiondevice according to the present specification for receiving the opticalmodulated signal. Moreover, the function for selecting which lightreceiver among the plurality of light receivers included in automobileB100 the reception device according to the present specification usesfor receiving the optical modulated signal may be included in thereception device or a device connected to the reception device.Moreover, the angle of the light receiver and the positioning of thelight receiver may be configurable.

Furthermore, the reception device described in the present specificationmay display, on the front panel included in the automobile or in thecockpit of the vehicle, a notification indicating that data has beenreceived. Moreover, the reception device described in the presentspecification may notify a user that data has been received by vibratingthe steering wheel of, for example, the automobile, or vibrating avibrator included on the steering wheel.

Moreover, an automobile including the reception device according to thepresent specification and the terminal may be connected via aninterface, and data obtained from the reception device may be stored instorage included in the terminal. Moreover, the automobile may alsoinclude a storage, and the automobile may store received data therein.Moreover, the storage included in the terminal and the storage includedin the automobile may both store received information.

In the present specification, a server may provide an applicationrelated to processes pertaining to the reception device, and thefunctions of the reception device according to the present specificationmay be implemented by the terminal installing the application. Note thatthe application may be provided to the terminal by the communicationdevice including in the transmission device according to the presentspecification connecting to a server over a network, and may be providedto the terminal by a communication device including a differenttransmission function connecting to a server over a network.

Similarly, in the present specification, a server may provide anapplication related to processes pertaining to the transmission device,and the functions of the transmission device according to the presentspecification may be implemented by the terminal installing theapplication. Note that a method in which the application is provided toa different communication device by the communication device connectingto a server over a network is conceivable.

Moreover, a server may provide software related to the light sourceincluded in the transmission device and the light receiver included inthe reception device, and transmission and reception of the opticalmodulated signal by the light source included in the transmission deviceand the light receiver included in the reception device, respectively,may be supported by obtaining this software.

Furthermore, the transmission device according to the presentspecification may function as a server, and an application included inthe transmission device may be provided to the communication deviceusing some communication means, and the reception device according tothe present specification can be implemented by the application obtainedby the communication device downloading the application.

Note that in the present specification, there is reference to a “lamp”and a “light source”, but the method may be a method of a projectordisplaying, for example, a still picture, moving picture, oradvertisement, and the optical modulated signal being included in thatlight. In other words, the “lamp” and a “light source” may includefunctions other than the emission of light. Moreover, the “lamp” and a“light source” may comprise a plurality of lamps and light sources.

Furthermore, the transmission method used by the communication devicethat generates an optical modulated signal and emits light may be amethod other than the transmission method described in the presentspecification. Moreover, the optical modulated signal may includeinformation other than what is described in the present specification.

Moreover, the lamp and/or light source, such as an LED lamp and/or lightsource, may itself include the functions of the transmission devicedescribed in the present specification.

Furthermore, the device that generates the optical transmissionmodulated signal may not include a lamp or light source, and may beconnected to a lamp and/or light source via an interface.

The communication method between the transmission device and thereception device described in the present specification and the presentembodiment may be the communication method illustrated in FIG. 31 .Hereinafter, FIG. 31 will be described.

The symbol mapper receives an input of transmission data, performsmapping based on a modulation scheme, and outputs a symbol sequence(ci).

The pre-equalizer receives an input of the symbol sequence, performspre-equalizing processing on the symbol sequence to reduce theequalizing processes on the reception-side, and outputs a pre-equalizedsymbol sequence.

The Hermitian symmetry processor receives an input of the pre-equalizedsymbol sequence, allocates sub-carriers to the pre-equalized symbolsequence to secure Hermitian symmetry, and outputs parallel signals.

The inverse (fast) Fourier transformer receives inputs of the parallelsignals, applies an inverse (fast) Fourier transform to the parallelsignals, and outputs inverse (fast) Fourier transformed signals.

The parallel serial and cyclic prefix adder receives an input of theinverse (fast) Fourier transformed signals, performs parallel conversionand adds cyclic prefix, and outputs the signal-processed signal.

The digital-to-analog converter receives an input of thesignal-processed signal, performs digital-to-analog conversion, outputsan analog signal, and the analog signal is emitted as light from, forexample, one or more LEDs.

Note that the pre-equalizer and the Hermitian symmetry processor neednot be included. In other words, there may be instances in which thepre-equalizer and the Hermitian symmetry processor do not perform theirrespective processes.

The photodiode receives an input of light, and obtains a receptionsignal via a transimpedance amplifier (TIA).

The analog-to-digital converter performs an analog-to-digital conversionon the reception signal, and outputs a digital signal.

The cyclic prefix subtractor and serial parallel converter receives aninput of the digital signal, subtracts the cyclic prefix, and thenperforms serial parallel conversion, and receives an input of parallelsignals.

The (fast) Fourier transformer receives inputs of the parallel signals,applies a (fast) Fourier transform to the parallel signals, and outputs(fast) Fourier transformed signals.

The detector receives inputs of the (fast) Fourier transformed signals,performs detection, and outputs a series of reception symbols.

The symbol demapper receives an input of the series of receptionsymbols, performs demapping, and obtains a series of reception data.

In this way, even when such a transmission device that transmits theoptical modulated signals and such a reception device that receives theoptical modulated signals are applied to the amendments according to thepresent specification, the embodiments can be implemented in the samemanner.

Moreover, the communication method between the transmission device andthe reception device described in the present embodiment may be thefollowing communication method.

Line Scan Sampling

An image sensor such as a complementary metal oxide semiconductor (CMOS)sensor is included in a smartphone or digital camera or the like. Forexample, the entire scene in a single image captured by the CMOS sensoris not captured at a single instant, but rather, for example, capturedline by line using a rolling shutter method, whereby the sensor readsout the amount of light received line by line. Accordingly, the amountof time required for the reading out is calculated, and exposure startand end times are controlled for each line by implementing a time delay.In other words, images captured by the CMOS sensor are constructed froma plurality of lines captured with a slight time lag between each line.

This exploits the rolling shutter effect of the CMOS sensor to allow foran improvement in visible light signal reception speeds.

In other words, in a first example of a visible light communicationscheme, as illustrated in FIG. 32 , utilizing the slight time lagbetween the exposure period of each line, the luminance and color of thelight source across a plurality of points in time can be calculated lineby line from a single image (image captured by the image sensor), makingit possible to capture a signal modified faster than the frame rate ofthe image sensor.

This sampling method is referred to as “line scan sampling”, and asingle row of pixels exposed at the same time is referred to as an“exposure line”.

Note that line scan sampling can be implemented using the rollingshutter effect of a CMOS sensor, but even when the rolling shuttereffect is implemented using a sensor other than a CMOS sensor, such as acharge-coupled device (CCD) sensor or an organic CMOS sensor, the linescan sampling can be implemented in the same manner.

However, in the settings used when capturing an image in the camerafunctions (capturing functions for moving or still images), even if arapidly flashing light source is captured, the flashing will not appearas a striped pattern extending along the exposure lines. This isbecause, with this setting, the exposure period is sufficiently longerthan the flash cycle of the light source, so, as illustrated in FIG. 33, the changes in luminance resulting from the flashing (light emissionpattern) of the light source are uniform, resulting in a substantiallysmall variation in pixel values between exposure lines, producing anapproximately uniform image.

In contrast, as illustrated in FIG. 34 , by setting the exposure periodequal to or slower than the flash cycle of the light source, the state(light emission pattern) of the flashing of the light source can beobserved as variations in luminance between exposure lines.

For example, the exposure lines are designed to extend parallellengthwise relative to the image sensor. In such cases, as one example,assuming the frame rate is 30 frames per second (fps), when theresolution is 1920×1080, at least 32400 samples are obtained per second,and when the resolution is 3840×2160, at least 64800 samples areobtained per second.

Line Scan Sampling Application Example

Note that the above described line scan sampling in which a signalindicating an amount of light received per line is read out, but methodsof sampling an optical signal using an image sensor such as a CMOSsensor are not limited to this example. A variety of methods that canobtain a sampled signal at a sampling rate that is higher than the framerate used to capture a normal moving picture, can be used as thesampling method to be used to receive the optical signals. For example,a method of controlling the exposure time per pixel and reading out asignal or a method of controlling the exposure time per group of pixelsarranged in a shape other than a line and reading out a signal may beused by utilizing a global shutter method that has a shutter functionfor each pixel. Moreover, a method of reading out signals a plurality oftimes from the same pixel in a period equivalent to one frame in theframe rate used in the capture of a normal moving picture may be used.

Frame Sampling

Furthermore, with a frame rate method that gives a shutter method foreach non-pixel, it is possible to sample optical signals even in amethod by which the frame rate is sped up.

For example, the present specification can be implemented in any of theline scan sampling, line scan sampling application example, and framesampling methods described above.

Light Source and Modulation Scheme

With visible light communication, for example, a light emitting diode(LED) can be used as a transmitter. LEDs are commonly used in lamps andin backlit light sources in displays, and can flash at high speeds.

However, light sources that are used as visible light communicationtransmitters cannot be allowed to flash uncontrolled when performingvisible light communication. If the changes in luminance made forvisible light communication are recognizable to the human eye, theoriginal functionality of a light source as a lamp will be lost.Accordingly, the transmission signal needs to be emitted at a desiredbrightness and needs to be imperceptible to the human eye.

One modulation scheme that meets these requirements is 4-pulse positionmodulation (4 PPM). As illustrated in FIG. 35A, 4 PPM is a scheme inwhich two bits are represented by a group of four time slots eachindicating either bright or dark light emitted by a light source.Moreover, as illustrated in FIG. 35A, in 4 PPM, each group of the fourtime slots includes three light slots and one dark slot. Accordingly,regardless of the content of the signal, the average brightness (averageluminance) is 3/4=75%.

For comparison, as a similar scheme, consider the Manchester codingscheme illustrated in FIG. 35B. In the Manchester coding scheme, one bitis expressed with two states, and the modulation efficiency is 50%,which is the same as 4 PPM, but among the two states, one is bright andone is dark, so the average luminance is 1/2=50%. In other words, 4 PPMis more suitable than the Manchester coding scheme as a visible lightcommunication scheme. However, since communication capability is notadversely affected by changes in luminance from visible lightcommunication that are recognizable to the human eye, depending on theapplication, there may be no problem in using a method in which thechanges in luminance are recognizable to the human eye. Accordingly, thetransmitter (light source) may use, for example, an amplitude shiftkeying (ASK) method, a phase shift keying (PSK) method, or a pulseamplitude modulation (PAM) method to generate the modulated signal andpulse the light source to emit light.

Note that the communication method between the transmission device andthe reception device described in the present specification is notlimited to the above example. Even frequency-based wirelesscommunication methods such as optical, visible light, infrared,ultraviolet methods can be implemented in the same manner. Moreover, inthe above description, an example is given in which optical modulatedsignals are received via an image sensor, but a photodiode may be usedin place of the image sensor to receive the optical modulated signals.Alternatively, a device other than an image sensor or photodiode may beused to receive the optical modulated signals.

In the present specification, a symbol related to location or positioninformation, a symbol related to time information, a symbol related toan SSID, a symbol related to an access destination, and a symbol relatedto an encryption key are described using the terminology “symbol”, butthese may be referred to as “data” or “information” or “field” or “bit”or “region” instead of “symbol”, and the embodiments can be implementedin the same manner. They may be referred to as something other than“data” or “information” or “field” or “bit” or “region” as well.Moreover, the transmission device may transmit any type of symbolconfiguration, such as a symbol related to location or positioninformation, a symbol related to time information, a symbol related toan SSID, a symbol related to an access destination, and a symbol relatedto an encryption key. What is important is that data related to locationor position information, data related to time information, data relatedto an SSID, data related to an access destination, data related to anencryption key is transmitted to the communication partner.

In the present specification, in the transmission device that includes,for example, a light source and/or lamp, the light source may becomprised of a plurality of light sources, and/or the lamp may becomprised of a plurality of lamps.

Supplemental Information 2 for Above Embodiments

It goes without saying that the embodiments described in the presentspecification may be combined with other aspects.

Moreover, the embodiments are merely examples. For example, while amodulation scheme, an error correction coding method (error correctioncode, code length, encode rate, etc., to be used), control information,etc., are exemplified, it is possible to carry out the presentdisclosure with the same configuration even when other types of amodulation scheme, an error correction coding method (error correctioncode, code length, encode rate, etc., to be used), control information,etc., are applied.

Regarding the modulation schemes, even when a modulation scheme otherthan the modulation schemes described herein is used, it is possible tocarry out the embodiments and the other subject matter described herein.For example, amplitude phase shift keying (APSK) (such as 16APSK,64APSK, 128APSK, 256APSK, 1024APSK and 4096APSK), pulse amplitudemodulation (PAM) (such as 4PAM, 8PAM, 16PAM, 64PAM, 128PAM, 256PAM,1024PAM and 4096PAM), phase shift keying (PSK) (such as BPSK, QPSK,8PSK, 16PSK, 64PSK, 128PSK, 256PSK, 1024PSK and 4096PSK), and quadratureamplitude modulation (QAM) (such as 4QAM, 8QAM, 16QAM, 64QAM, 128QAM,256QAM, 1024QAM and 4096QAM) may be applied, or in each modulationscheme, uniform mapping or non-uniform mapping may be performed.

Moreover, a method for arranging 2, 4, 8, 16, 64, 128, 256, 1024, etc.,signal points on an I-Q plane (a modulation scheme having 2, 4, 8, 16,64, 128, 256, 1024, etc., signal points) is not limited to a signalpoint arrangement method of the modulation schemes described herein.

In the present specification, conceivable devices that include the radiodevice described in the present specification include a communicationsand broadcast apparatus, such as a broadcast station, a base station, anaccess point, a terminal or a mobile phone, or a communication apparatussuch as a television, a radio, a terminal, a personal computer, a mobilephone, an access point, or a base station. Moreover, the radio devicedescribed in the present specification is conceivably a device havingcommunication functions that is connectable via some interface to adevice for executing an application in, for example, a television, aradio, a personal computer or a mobile phone.

In the present specification, conceivable devices that include thereceiver described in the present specification include a communicationsand broadcast apparatus, such as a broadcast station, a base station, anaccess point, a terminal or a mobile phone, or a communication apparatussuch as a television, a radio, a terminal, a personal computer, a mobilephone, an access point, or a base station.

Moreover, in the radio-wave communication radio device according to thisembodiment, symbols other than data symbols, such as pilot symbols(preamble, unique word, post-amble, reference symbol, etc.) or symbolsfor control information, may be arranged in any way in a frame. Here,the terms “pilot symbol” and “control information symbol” are used, butthe naming of such symbols is not important; the functions that theyperform are.

A pilot symbol may be a known symbol that is modulated using PSKmodulation in a transceiver (alternatively, a symbol transmitted by atransmitter can be known by a receiver by the receiver being periodic),and the receiver detects, for example, frequency synchronization, timesynchronization, and a channel estimation (channel state information(CSI)) symbol (of each modulated signal) by using the symbol.

Moreover, the symbol for control information is a symbol fortransmitting information required to be transmitted to a communicationpartner in order to establish communication pertaining to anything otherthan data (such as application data) (this information is, for example,the modulation scheme, error correction encoding scheme, or encode rateof the error correction encoding scheme used in the communication, orsettings information in an upper layer).

Note that the present disclosure is not limited to each exemplaryembodiment, and can be carried out with various modifications. Forexample, in each embodiment, the present disclosure is described asbeing performed as a communication device. However, the presentdisclosure is not limited to this case, and this communication methodcan also be used as software.

Note that a program for executing the above-described communicationmethod may be stored in read only memory (ROM) in advance to cause acentral processing unit (CPU) to operate this program.

Moreover, the program for executing the communication method may bestored in a computer-readable storage medium, the program stored in therecording medium may be recorded in random access memory (RAM) in acomputer, and the computer may be caused to operate according to thisprogram.

Each configuration of each of the above-described embodiments, etc., maybe realized as a large scale integration (LSI) circuit, which istypically an integrated circuit. These integrated circuits may be formedas separate chips, or may be formed as one chip so as to include theentire configuration or part of the configuration of each embodiment.LSI is described here, but the integrated circuit may also be referredto as an integrated circuit (IC), a system LSI circuit, a super LSIcircuit or an ultra LSI circuit depending on the degree of integration.Moreover, the circuit integration technique is not limited to LSI, andmay be realized by a dedicated circuit or a general purpose processor.After manufacturing of the LSI circuit, a field programmable gate array(FPGA) or a reconfigurable processor which is reconfigurable inconnection or settings of circuit cells inside the LSI circuit may beused. Further, when development of a semiconductor technology or anotherderived technology provides a circuit integration technology whichreplaces LSI, as a matter of course, functional blocks may be integratedby using this technology. Adaption of biotechnology, for example, is apossibility.

Note that in the present specification, for example, in Embodiments 4,5, 6, and 7, an encryption key for a terminal to connect to a basestation over radio waves is described, but the encryption key is notlimited to an encryption key for connection over radio waves.

For example, assume the base station is connected to a network and theterminal communicates with the network via the base station. In suchcases, the encryption key may be an encryption key for the terminal toconnect to the network. Accordingly, information on an encryption key isincluded in the optical modulated signal described in the presentspecification, and even in this cases, the embodiments can beimplemented in the same way, and the same advantageous effects can beachieved.

Moreover, the optical modulated signal may include at least one of anencryption key for connecting with a base station (for example, anencryption key for an SSID) and an encryption key for connecting to anetwork.

Although only some exemplary embodiments have been described above, thescope of the Claims of the present application is not limited to theseembodiments. Those skilled in the art will readily appreciate thatvarious modifications may be made in these exemplary embodiments andthat other embodiments may be obtained by arbitrarily combining thestructural elements of the embodiments without materially departing fromthe novel teachings and advantages of the subject matter recited in theappended Claims. Accordingly, all such modifications and otherembodiments are included in the present disclosure.

INDUSTRIAL APPLICABILITY

The present disclosure is applicable to a wide range of communicationsystems that transmit and receive optical modulated signals.

The invention claimed is:
 1. A receiving method comprising: receiving,at a terminal, a light signal transmitted from a light transmissiondevice; demodulating the light signal to obtain first data, the firstdata including an identifier of a wireless transmission device and alocation identifier of the light transmission device; receiving, at theterminal, a wireless signal from the wireless transmission device; anddemodulating the wireless signal to obtain second data, the second dataincluding map data including the location identifier of the lighttransmission device, wherein the receiving and the demodulating of thewireless signal are performed after the receiving and the demodulatingof the light signal, based on the identifier of the wirelesstransmission device obtained by receiving and demodulating the lightsignal.
 2. A receiving apparatus comprising: a light signal receiverthat, in operation: receives a light signal transmitted from a lighttransmission device; and demodulates the light signal to obtain firstdata, the first data including an identifier of a wireless transmissiondevice and a location identifier of the light transmission device; and awireless communication device that, in operation: receives a wirelesssignal from the wireless transmission device; and demodulates thewireless signal to obtain second data, the second data including mapdata including the location identifier of the light transmission device,wherein the receiving and the demodulating of the wireless signal areperformed after the receiving and the demodulating of the light signal,based on the identifier of the wireless transmission device obtained byreceiving and demodulating the light signal.